Give him a moment to process this new information.

The turtles were mutated with human DNA. Fair enough. Leo's body certainly is more reminiscent of a human's than the squatty stature of a turtle. Akechi shuts his eyes, grips his chin, and exhales through his nose. Fair enough.

Rescuing children from a life of servitude... it's noble, certainly, but a rat. The man turned into a rat.

"...So how exactly did he mutate?"

There are missing details, but for as baffling as it all sounds, he can't deny its intrigue.