In accordance to the last page, it does almost sound like a oneshot of Karakai Jouzu no (Moto) Takagi-san showing the somewhat future version of Chi. Considering Takagi never acted like this and Chi does all the time. Though, it could also just be a joke hinting that Chi's life through school is going to be just like theirs I suppose. Kind of feels this should be part of moto but I guess it could be fitting in either.