Sabitsuki is the main character of .flow, who is controlled by the player. Much like the protagonists of Yume Nikki and Yume 2kki, she spends the game wandering around her mental landscape and collecting a multitude of effects. Similarly, not much is explained about her past, or about the things she sees in her dreams.
- Sabitsuki's name continues the tradition of giving fangame characters a name ending in -tsuki. However, the kanji in Sabitsuki's name have a different meaning than the ones in Madotsuki's name. Sabitsuki means "covered in rust".
- It is theorized that the shape on the title screen of .flow is a very abstract depiction of Sabitsuki herself.
- If it is to be inferred that Sabitsuki, Smile, and Sister are all related the difference in hair color could be a side effect of the "cure" she and the other test subjects were given as all the Kaibutsu's also seem to have white hair as well.
- It is theorized that Sabitsuki is slowly losing her mind either from the disease or from side effect of her treatments.
- The Kaibutsu also seem to have lost their mind as well (active chasing ones) or are on the verge of losing them (normal ones that will become active after hitting) which could further link that both Sabitsuki and the Kaibutsu are suffering the same disease/side effects from disease treatments.
- Sabitsuki didn't fit in much at school and was either widely ignored or made fun of. Support for this theory is that going through the corrupted school Kaibutsu will actively chase you with pipes as they their laughter fills the halls.
- The reason that Sabitsuki doesn't want to leave her room may imply that she is quarantining herself because of a disease that she has.