I read a really manga before but I just can't manage to remember its title. There's a man keeping a white pretty cat. One day he picked up an injured black cat and the cats became friends. The man died later on leaving the two cats with the neighbor girl. The cats ran away from home to find the man's grave and one of them got run over by a car.

Does anyone know which manga is this? Please help me > < I really want to read it again.

I think it's one of the character backstories of Gakkou no Sensei

OMG THANK YOU SO MUCH > <