[Chirst]

Volume 4 Chapter 13 is out at Bakatsuki
More spoil from Oilman on FB about Yotsuba Maya

Spoiler for spoil:

what they did to tetsuya was a different experiment.
you're talking about a 12 years old who got kidnapped, raped experimented on; her mentality couldn't handle it so miya used her magic to flip all her experience or memory into knowledge as her magic can't distinguish different memories from each other. so to not let the same thing ever to happen again yotsuba introduce the guardian system.

btw when maya was kidnapped saegusa kouichi(mayumi's father) lost his right eye. then when he heard about what happened to maya's losing reproductive capability and their engagement got canceled; he refused to use cloning tech to restore his right eye as it felt it's not fair for him only to appear as nothing happen while his lover(maya) loses remain.

to get revenge on what happened to maya her father and the leader of yotsuba at that time assaulted the kidnapping country. as a result; yotsuba lost 30 men on there side halving yotsuba power. on the other side that country or lab lost 4,000 military personal and magicians
-Oilman