YAWARAKA SANGOKUSHI TSUKISASE!! RYOFUKO-CHAN

Ryofu Housen (Lu Bu) is a powerful general from the Three Kingdoms; alongside Chinkyuu (Chen Gong), Ryofu suddenly finds himself falling to Earth, and landing... in the body of an elementary school student?! With their new lives as flat-chested, women-loving children, Ryofu and Chinkyuu follow their hunger and their desire to get back to their old lives somehow; but it will be difficult, given the variety of obstacles in their way including old enemies, epic monster battles and the most important thing of all, trying to get their hands on Eri-sensei's mammoth F-cup breasts! — Description from AniList community (anilist.co).