In his house with 'Sister', he can grant you the Smile Menu. On the balcony at the top floor of the school, he appears in full-sized sprite form and you can grab the Tattoo effect. He also appears in different rooms around the school and during the Corrupted School Event.
Smile was named after the file name containing all his sprite info, "smile.png".
The implied history between Sabitsuki and Smile is a common interest point amongst fans.
Smile has long spiked black hair in a similar style to Sabitsuki, and has distinctive "tattoos" on his eyes.
Smile is seen wearing a dusty brown vest-like jacket with a red shirt underneath, long dark grey jeans, black shoes, and what appears to be bandages on his wrists/lower arms.
- When you hit Smile with the pipe he actually speaks. He also laughs and you can hear the Kaibutsu giggle as well.
- As of version 0.15 you can now kill Smile during Rust's version of the Corrupted School event. Previously he was the only NPC unable to be killed, apart from the Kaibutsu.
- Smile is the only significant boy in .flow aside from Doctor-san.
- it is speculated that Smile is a self-insert character by lol, as he resembles him in a picture he uploaded of himself. Both of them have similar hair and clothes. His laughter is also lol's own voice, thus adding to this theory.
- There is speculation that Smile and Sister are related to Sabitsuki in some way, either by blood or relation.
- Another theory is that Smile was one of her friends who she might have grown up with. Sabitsuki trusted Smile who betrayed her trust as they grew up. The fact that he's surrounded by school children could indicate that he became popular and perhaps eventually snubbed Sabitsuki altogether.
- Smile appears to be very protective of Sister, as pulling out your pipe will lead to him pulling out his weapon as if protecting her as she hides behind him. Perhaps his protectiveness of his sister lead to him not being friends with Sabitsuki anymore because he didn't want her hanging around his sister with Sabitsuki's disease getting progressively worse.
- A possible theory may be that Sabitsuki and Smile have committed some sort of crime together. This could possibly explain the "Black Hood" and "Iron Pipe" effects. Smile also, of course, smiles when you hit him, possibly reminiscing on the act they performed. This could also explain why the Kaibutsu are so bloody and explain why Smile is in one of the school rooms alone with his hammer, as all the children flee from him. When he fights back during the corrupted school event, it could be an act of betrayal, for many unknown reasons. Sister seems to be afraid of Sabitsuki, possibly explaining this further.