Every time I see the 4th panel, I imagine "Level Up!" appearing above their heads.

yes this age is very hard lD
I like the story...but not sure for making the translation...

Len grew boobies?

I think he's looking down his pants.

Kaito: *so small* HAHAHAHA
Len:STFU

Kaito just broke Dude Rule #2: Don't make direct eye contact with another guy's junk.