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 a foreign 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 the same incident. UA was attacked by a Villain's Quirk possessing a similar power.

Ability/Quirk: Starters/Enders

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

Hopefully, nothing would go wrong…

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 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. Being used to Yosano-sensei's sadistic grin, it looked completely out of place on the doctor's face.

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 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, he got his answer.

To his shock and amazement, he watched as the injured areas on his body lit up in a glow radiating soothing green light. Within a span of a few seconds, the cuts and bruises disappeared as though they had never happened. However, he felt sleepy and exhausted afterwards, like he had just ran a marathon.

Chiyo giggled girlishly at the white-haired teen's confusion as she reached into her desk for her bag of gummies. "And treatment success. Now be more careful next time, okay. Do your best to not get hurt the next time you'd like to see me. Here, have some candy before you go."

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 treatedt, but this time, his visit wasn't so bad at all.

(BNHA Era)

"-makes sense as 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." Up until now, she never had someone react so positively to her Ability like Midoriya Izuku. It was very refreshing to meet someone who can appreciate her efforts.

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 on one of the beds (wait, that's actually blood) was a sizable butcher knife with red liquid still stained on the gleaming metal.

"Nevermind, I don't want to know," 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 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 kisses afterwards, 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 see him being chased down the halls by a chainsaw wielding 4-foot-tall old lady. But I ended up writing this instead.

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