help me pls! this oneshot manga has been childhood and the best manga that I ever read. I cried 3x cause how sad it is..

I forgot the manga name but I still remember a bit how the story goes.

it goes about a kid who have blood cancer and his mom took care of him on the hospital, one day he got invited to a company to became their boss for a day, once he got into a meeting about the design for the company rooftop and that kid told them to design it whale and that’s his favorite!

and that kid favorite drink is like chocolate drink? I think? with bottle of can and he likes swimming. the story is sad and that kid died after one of his brother gave him his favorite chocolate drink and took a sip, he had a tears in his eyes and told him the drink is tasty.. sorry for bad grammar and wacky sentence because i write this at 11 am!! help would be appreciated