Seeing Lida's transponder go off Izuku quickly headed towards his location as fast as he could as he flew through the city he could see it was in chaos fire and nomu’s everywhere.

Batman: (i need to find lida first then i can deal with the nomu’s)

As he got close to Lida's location he places the batmobile on autopilot and ejects out of the batmobile dropping on a building overlooking an alley far away from the events happening in the center of the city. He lands on one of the buildings before looking over the edge seeing a man covered in weapons with a red scarf standing over lida ready to bring down a sword.

Acting fast Izuku dove towards the man as he dove, he threw a batarang knocking the sword out of his hands before Izuku kicked him away from lida. As he lands he immediately checks on lida.

Batman: “you ok?”

Lida: “i'm fine but ever since he cut me i can't move my body…i think it’s his quirk”

While lida was talking Izuku look around the ally spotting a hero slumped against the wall

Batman: (if it’d just been lida i would have been able to fly him out of here but with the other hero here. The only option i have is to ever beat him or stall till some other heroes arrive)

Lida: “batman just take native and get out of here”

Batman: “and leave you to die not going to happen”

stain: “It doesn't matter i have a duty to kill them, it doesn't matter if it's now or later. All the fakes must die”

Izuku stands up before turning towards stain

Batman: “What do you mean by fakes?”

stain: “fake heroes like you. You wear the mask and use the mantel of a true hero but without them you would be nothing”

Without another word he threw a knife which Izuku intercepted by firing a batarang knocking it away. They both ran at each other. Stain swung one of his swords trying to cut Izuku before the sword could hit him; he catches and breaks it with his forearm blades before elbowing him. He knocked stain back a couple feet only for him to pull two blades out before running back towards Izuku he jumped up bringing both the blades down before they hit him he jumped back avoiding both the blades. Izuku quickly shot his grapple at him as soon as it attached to him he pulled as hard as he could causing stain to go flying towards him when he was close Izuku stuck his arm out clotheslining him. Stain gets up and slashes Izuku on the back of the leg causing him to fall to one knee holding his leg in pain. The hero killer licks the blade, freezing Izuku in place. As soon as he is frozen stain walks towards him

stain: “you're not batman your just another fake playing dress up pretending to be a true hero”

He held the sword to his throat. As he pulled the sword back ready to thrust it forward and impaling him. As he tried something stopped the sword inches away from Izuku's throat. All of a sudden the sword flew out of stain and embedded itself in the ground a few meters away. Everyone looked around until a familia green haired girl dropped down into the alleyway.

Izumi: “is everyone ok lida? Native? Batman?”

Batman: “What the hell are you doing here!?”

Izumi: “i was doing my work experience with a hero and he told me to make sure that none of the nomu’s made it further out of the city and well i saw this going on so i thought i should help”

After saying this she faced stain before she could do anything. A knife flew past her cutting her cheek she looked back at him only to see he was directly in front of her acting on impulse she used her quirk to propel him away from her. As this was happening Izuku started to be able to move his body again. Stain throws three blades towards her only for three batarangs to knock them away before stain could look at the direction of the batarangs. Izuku tackled him into a wall.

lida: “how can he move again”

Izumi: “does his quirk have a time limit”

Native: “it can’t he was the last one he got”

As they hit the wall the hero killer kneed Izuku in the stomach before pushing him away. Izuku jumped back landing next to Izumi 

Batman: “his quirk works by digesting a person's blood after that it prevents the person from moving. As far as i can tell the time limit depends on the type of blood the person has” 

Native: “blood type?...mineis b”

Lida: “im type A”

Stain: “blood type?...that's correct”

Izumi: “we can't really do much just by knowing his quirk”

Batman: “i might be able to take him but i can't do that while also defending those two”

He looks her directly in the eye before continuing

Batman: “i need you to take them both get them some medical attention get the attention of any pro you can find and bring them here”

Izumi: “but what about you”

Batman: “don't worry about me i’ve taking a lot of punishment over my life time”

She was about to say something when

Batman: “look for once im trusting you NOW GET THEM OUT OF HERE!!”

She just nodded before using her quirk to grab both native and lida before flying away.

Batman: (i can't leave myself open. My best option is to keep him at a distance get too close and those blades could cut me into ribbons)

Stain: “one-on-one huh? It won't be easy”

Batman: “it never is”

After saying this they start running at each other as he was running at stain he pulls out two electric batarangs one for each hand when they get close stain swings his sword only to be blocked by Izuku using the batarangs. They start pushing against each other trying to get the upper hand. As they did this Izuku activated the batarangs releasing an electric shock from the batarangs into the blade enough to cause stane to let go of the blade and back up a couple feet immediately Izuku threw both the batarangs at him. Only for stain to dodge them both they glare at each other before going at it again as they get close Izuku tries to kick stain in his ribs only for stain to grab his leg before it could hit him. Before anything could happen Izuku jumps up and spins using his other leg to kick stain in the face making him let go of his legs. He quickly picks himself up and makes distance between each other.stain ran up to him he grabbed a knife before getting ready to stab him before the knife could reach him Izuku slammed his forearm against stains stopping the knife from getting any further this struggle continued for a couple of seconds until stain dropped the knife into his other hand he thrust the knife forward Izuku quickly moved only getting slashed in the side. Izuku dropped back holding his side as stain brought the knife to his mouth before his tongue could touch the blood on the blade. Izuku quickly shot a batarang knocking the knife away from him.

Batman: (close combat isn't working out how i hope)

Stain: “you're just what i thought you were nothing but another fake a cancer on this society”

Batman: (i need to think of a better way of fighting him the direct approach isn't working)

As Izuku stands up he grabs a pile of pellets out of his utility belt. Seeing this stain immediately sprinted at him before he could get close Izuku threw them on the ground as soon as they made contact a thick cloud of smoke filled the alleyway preventing anyone from seeing. As stain got close he tried to slash Izuku but only managed to hit nothing but smoke. He looks around the smoke obscuring his vision everywhere he looks he was about to move until he was struck in the back when he swung his sword back there was still nothing but smoke.

Stain: “come out and face me like a true hero would!!”

Batman: “but according to you i'm not a hero”

As he spoke his voice echoed throughout the alleyway making it difficult for stain to pinpoint his location. This was until he heard the sound of something moving as soon as he heard this he threw his sword at the noise when he got close all he saw was just a pile of boxes as he was about to move he reserved a kick to the stomach after that stain started swinging in random directions trying to hit him. The moment he stopped he proceeded to be uppercut causing him to stumble back as he hit the wall he quickly jumped passing the smoke and embedded his sword in the wall before perching on top of it watching the smoke for any movement.

With Izuku

As he was hiding in the smoke he had his detective vision on seeing stain through the smoke. After hitting him he watched stain leap through the smoke and perch on his sword.

Batman: (this might be my last chance)

He gets in position under where stain is perching as he gets under him he activates his  rockets propelling him towards stain as fast as he unfortunately doing this revealed his location to stain. As he built up speed stain pulled the sword out off the wall and leaped towards him ready to slash Izuku as they get closer stain pulled back his sword while Izuku pulled one fist back as they get even closer stain starts moving the sword towards him when they get close to each other stain thrusts his sword forward acting quick Izuku leans away as he hit stain causing stain to fall to the ground as Izuku lands he sees a cut across his chest. He looks over at stain seeing him lying on the floor

Batman: (he has to be knocked out after all of that…right? Hopefully)

He proceeds to search stain removing all the weapons he could find before tying him up and dragging him to the streets. As he walked to the street all his adrenalin started to wear off causing him to start to move slower. When they make it to the street Izuku starts disposing of all the weapons which have his blood on them. After a while he was leaning on a wall next to a tied up stain waiting for the police or pros until he heard a rush of what sounded like a group of people heading in his direction as he looked towards the sound he saw the group consisted of Izumi, Todoroki and several pro heroes he steps in front of the group.

Izumi: “BATMAN!! I brought the heroes here as fast as i can is everything ok”

Gran torino: “my boy are you alright those wounds look quite severe”

Batman: “i'll be fine until i can get medical attention”

Hero 1: “i’ll call an ambulance right away”

Batman: “i’ll be fine don't worry about me the person you should be worrying about is him”

upon saying this he steps aside revealing a tied up stain

Hero 2: “h-hey is t-that”

Hero 3: “don’t tell me…it’s the hero killer”

Hero 1: “I'll call the police!”

Izumi: “you defeated the hero killer by yourself!”

Batman: “not bad for a quirkless…is it!!”

As he says this he gives her a scowl

Izumi: “n-no t-thats not what i meant”

Batman: “forget it i'll leave stain with all you and the police”

Izumi: "b-but i really didn't mean it to come out like that i...i'm sorry"

Izuku just gives her a quick look before calling the batmobile to him as it arrives he slowly walks to it Before getting in and heading back to the batcave to get patched up by bruce after a while he heads back out to hosu general hospital

At hosu general hospital

In the hospital lida was sitting on his bed deep in thought until he felt a hand on his shoulder when he looked he saw nothing until he heard similar clicking sound after the sound Izuku turned visible again

Lida: “Batman, why are you here?”

Batman: “i came to see if you were ok you lost a lot of blood in that alleyway”

Lida: “i'm fine they gave me a blood transfusion i now have to wait for my consequences”

Batman: “well every action does have its consequences”

As they were talking the door to the room opened revealing two people, Manual and a tall man with a dog’s head they both gave a relatively shocked look when they saw Izuku sanding there before they could say anything lida walks up to manual and bow’s 

Lida: “i am truly sorry”

Manual slowly shakes his head before responding

Manual: “all right. You’ll cause trouble for others!. If you understand then never do it again!”

Lida: “i won't”

Manual: “good!. Now that it’s all sorted let me introduce the chief of police”

He gestured to the man beside him

Chief: “In any other case your actions would get you expelled out of the hero course but due to the event’s of tonight we had chosen to bend the rules a little. You may stay in the hero course but step out of line even once and you will never be able to be a part of any hero course. Do I make myself clear!”

Lida: “yes sir”

Chief: “good now as for you”

He looks directly at Izuku as he continues

Chief: “you will receive credit for your work with the hero killer and as someone who also protects the peace i personal thank you”

Batman: “you don’t ever have to thank me”

After saying this he went to the window where he jumped into the batmobile and headed back to the batcave as soon as he made to the cave he got out of the batmobile and headed to the chair when he reached it he pulled off his mask and slouched on it with a look of exhaustion on his face the only thing that kept him awake apart from the pain he was feeling from the long night was the same thought that has been plaguing his mind since the beginning of the day whether he should tell uraraka his identity. While he was in thought Bruce walked back into the cave finding him.

Bruce: “where the hell did you go?”

Izuku: “i could ask you the same question”

Bruce: “business call the sound of bat’s would most likely raise some suspicion”

Izuku: “i went to make sure lida wasn’t dead”

Bruce: “and do you want to explain why you not back at ua resting”

Izuku: “i was…thinking about something”

Bruce: “And that was?”

Izuku: “.....ochako….”

Bruce: “you want to tell her”

Izuku: “i…i d~”

Bruce: “it's late go home”

Bruce started walking to the entrance leaving Izuku in the cave before he leaves the cave fully he stops

Bruce: “These decisions are yours to make make them wisely”

This comment made Izuku pause as Bruce left the cave. After a couple of minutes he headed back to ua to recover from the night.