Jin is a new unit introduced in Metal Slug Attack.
A samurai hailing from the same village as Yoshino, she eventually left on her own so that she could train alone to become stronger.
She initially disliked living with other people, though she does not mind being with animals. In fact, she has a pet monkey which she named Asajiro.
It is speculated that she fell in love with Red, and is the mother of Licht and Elena. In the Extra Ops "Cross Over Fate, Ptolemaios taunts the two by stating that he killed their parents, something which is mentioned in Another Story as Jin helps Red train so he can battle the Ptolemaic Army. Elena's MSA description also states the swords she uses is a keepsake of her mother's, which function similarly to Jin's.