Disclaimer: I have no rights to Bungou Stray Dogs and Boku no Hero Academia. What you are about to read is the result of a bored fanfiction author with a plotbunny to raise.

Summary: In Yokohama, the Armed Detective Agency had recently dealt with a case involving an American tourist by the name of Lissa Price, who had lost control of her Ability and hit an unknown amount of people with it. Decades later, Mustafa suffered a similar incident when UA was attacked by a Villain's Quirk possessing the same power.

Ability/Quirk: Starters/Enders

The person afflicted with it would have their consciousness swapped with one of their future/past incarnations and/or descendants/ancestors. The respective powers of the individuals also carry over despite being in another body. However, exactly when the Ability/Quirk will take effect and how long it lasts is completely at random.

Hopefully, resolving the issue would go smoothly…

Right?

Switch 1: Yasano Akiko and Shuuzenji Chiyo

(BSD Era)

"Oh dear, you've had a rough day, haven't you?" Chiyo-sensei tsked as she took in the injuries Atsushi had recently obtained.

"Y-yes, ma'am." Atsushi squeaked in terror. The old woman inhabiting the doctor's body was related to Yosano-sensei somehow. No doubt she has some sort of amazing but trauma-inducing healing Ability.

"Now stay still. It'll all be over before you know it." Chiyo-sensei said cheerfully with a kind look in her eyes and a comforting smile. It looked completely out of place on the doctor's face, whose pretty features were usually twisted into a sadistic grin.

As she got closer and closer to him, Atsushi stared at the body-swapped Youthful Heroine in horror, and the dread polled into his stomach.

Her lips puckered up and…

CHUUUUU~!

Atsushi blinked in confusion for a few moments. Did… Did she just kissed him on the forehead? Just as he was about to voice his confusion, Chiyo-sensei's Ability worked its magic.

To his shock and amazement, he watched as all the injured areas on his body lit up in a soothing green glow. Within a span of a few seconds, the broken bones and lacerations he had sustained on his last mission disappeared as though they had never happened. As soon as the light faded, he felt sleepy and exhausted, like he was in desperate need of a nap.

Chiyo giggled girlishly at the white-haired teen's confusion as she reached into her desk for her bag of gummies. "Treatment success. Now be more careful next time, alright? Here, have some candy before you go, Atsushi-kun. They'll help you recover some of that lost stamina used while healing you."

Atsushi took the offered gummies with a grateful bow as he exited the office. Normally, he dreaded having to visit Yosano-sensei to get his injuries treated, but this time, the visit wasn't so bad.

He's going to miss Chiyo-sensei when she finally leaves.

(BNHA Era)

"-you are the first doctor to have a healing Quirk legally recognized by the government. By setting a precedent, you opened doors for the application of Quirks into the medical field. Your legacy laid down the foundations of Heroes specializing as battlefield medics. Thou Shalt Not Die is essentially Quirk history's first combat-oriented healing Quirk."

Yosano giggled as the green-haired boy continued to ramble. "You are one weird kid, you know that. Thanks for the compliments. I think you're the first patient to want to be treated by me." It was very refreshing to meet someone who can appreciate her efforts.

Up until now, she never had someone react so positively to her Ability like Midoriya Izuku and so many others. As soon as he saw her Ability in action, he quickly deduced her identity. Who knew that Yosano Akira would be regarded as such an important historical figure in this era despite her sordid past?

The door to Recovery Girl's office opened, revealing Todoroki. "Midoriya, is Yosano-sensei done with healing you? Present Mic sent me to-"

His words died as soon as he saw the massive pool of blood on the floor. Lying on top of the crimson sheets (wait, that's actually blood) of one of the beds was a sizable butcher knife with red liquid still dripping off the gleaming metal.

"Nevermind," Todoroki deadpanned as he slowly backed out from the crime(?) scene.

(Deleted Scene)

(*Toshinori barges into the teacher's lounge*)

Cementtoss: "All Might? Why are you so out of breath?"

Toshinori: "QUICK, HIDE ME! DON'T LET HER KNOW I'M HERE!" (*dives underneath a table*)

(*Yosano walks past the room*)

Yosano: (*singsong*) "Oh, Toshinori-kun~ Where are you~? Come out, come out, wherever you are~. You're long overdue for a checkup~" (*revs up chainsaw*)

…

…

Midnight: "And you people complain about my dominatrix persona."

AN: I can't help it. The ADA will definitely be missing Chiyo and her healing kisses after Starters/Enders ran its course, and Shouto will never look at the nurse's office the same way again. Originally, Yosano (in Recovery Girl's body) was going to go berserk upon seeing Toshinori's emaciated form, and the students are going to witness seeing him being chased down the halls by a chainsaw wielding 4-foot-tall old lady, but I ended up writing this instead.

Edited: 11/4/2019

This is a self-indulgent crossover fic. I had a brain fart, and this is what I came up with. So just read, enjoy, and don't take it too seriously. Thank you for your time~ * ・・(o_ _)o