Forgot title manga

Hey guys,
so there is this manga (one of the few straight ones I've read.)
and I totally forgot the title but I do remember the whole plot.

So basically, this girl and her little brother get left behind with their grandma by their dad. The grandma falls from the stairs and dies. The two kids have no idea what to do so they just bury them in their backyard. Somehow this guy from the girl's class gets involved. They lowkey start to live together, but of course, the girl and the bro tell him nothing about it till he does find out.
They're all reallyyyyy young. If it helps I can also tell you the ending, but other than that, that's literally everything.

To the person who knows what I'm talking about, please tell me. it would mean a lot to me. (づ￣ ³￣)づ