Chapter 124: Ombusman
Rin's mind is so powerful the vampire cat boy she imagined is one of the best things I've seen I have no notes thank you Rin.
According to Seiko, Rin is being haunted by an ombusman. Traditionally, that yokai is called the konaki-jiji (crying old man), which takes up the appearance of an old man or baby. It lures people to pick it up, then becomes a heavy stone that crushes its victim to death. No idea where ombusman comes from though. The name for this yokai in the Japanese version is オンブスマン (onbusuman), which may be a combination of "onbu" (piggyback), "busu" (ugly), and man, but who knows lol.
The Ombusman is Mai's spirit that got transformed, but it can also be seen as the manifestation of the pressures Rin feels in her life. The responsibility of taking care of her family at such a young age, wanting to pursue a dream with her friends but not being able to, and what gets revealed in the next chapter..... She has gone through a lot.