A strange four-year-old boy named Kotaro moves into Shimizu Apartment all on his own. He doesn't seem to have any parents or family around.

When he sees someone handing out free balloons, Kotaro tries to collect as many as he can. But there's a reason he wants so many balloons.

Kotaro's friend Kakeru has a maid who takes care of everything for him, so Kotaro decides to show Kakeru how to do things for himself.

For some reason, Kotaro is very particular about his tissues. He wants expensive, soft ones because they're "sweet." Later, Karino figures out why.

A man named Aota moves into the building for a month. When he asks Kotaro to be his friend, Karino gets suspicious — and a little jealous.

A girl named Kana starts coming over to Kotaro's house to play everyday after kindergarten, but she never seems to have fun.

Karino brings Kotaro and all his friends to the movies. Kotaro wants to see the new Tonosaman film, but the other kids want to watch something else.

Whenever Kotaro goes to see the neighborhood dentist, Dr. Ohba always takes the time to talk to him and ask him lots of questions.

One day, a woman Kotaro doesn't recognize comes to pick him up from kindergarten. She says she's Karino's ex-girlfriend.