grandpa is already my favorite character. i'm a big fan of the "weirdo artist" and "kindly and helpful old person" archetypes, so he's got quite a few bonus points. he's a great foil to both of the kids too.
i don't know how to explain it, but the manga feels kind of shojo-y? not really the art so much, but the dialogue and the characters feel very different than the usual shonen protags. if you gender swapped the cast so far and changed the art style, i don't think i'd be fazed in the slightest if you told me it was shojo.
i'm already excited to read the next chapter. i hope they'll explain why this dude basically has a sharingan for art 💀