Ken to Mahou to Gakureki Shakai - Vol. 1 Ch. 7.5 - Don't Bully My Sister!!

[MangaDex]

 

[deathmailrock]

On that day, he won her heart and gained her training...

 

[not_yamato]

Good thing these kids never got the elfen lied treatment.

 

[orangerain7734]

Ohhh, so it was the sister who put him through hellish training, not the mother. That explains how he reacted to her ambush so well much later.

 

[welcome2atlantis]

She didn't need any protecting! It was actually the other way around!

 

[pandatime]

I see
the sis had just been mercyfull the whole time

 

[IvanDFakkov]

Her fists are rated E for everyone

 

[Nyaaa]

This makes sense lol

 

[jean-chuck]

Never touch the little brother of a brocon older sister, NEVER!!!