Marin is a fellow schoolmate of Raya and Atma who is a reserved and quiet girl who dedicates herself to assisting in the school library. It is revealed in Chapter 4 that she is the one who gifts Atma the red book and magic wand.
Additionally, Marin have a childhood connection with Nirmala, who is also known as Raya. In Chapter 4, Marin joins Atma in their quest to find Raya. The climax of the chapter unveils a surprising transformation as Marin metamorphoses into a snail and it was simply erased by Raya.
In the real world, she appears as a college student who is already working as a book writer.