Ryuu's manga / #boss x subordinate(1)

this is awesome. his boss became a child one day because ml wished to become young and change his past but he didn't travel back in time, he just turned into a child. So, the mc helped him throughout the whole story while the ml grows up every time he gets a fever and then ml meets his childhood crush whom he wanted to fix his past with but realized that it was only a joke to him even tho ml actually fell for him. mc learned all of it and still stayed together with him.