I got a request a while back for the design of Rin's mom, and I finally did it!
She was a very caring and compassionate person who just so happened to be in the wrong place at the wrong time when she met Poseidon. She protected Rin for as long as she could after she was born, but unfortunately — after Rin turned 3 and her Quirk manifested early — Poseidon no longer had a use for Rin's mother and "got rid of her," as she was only used for childcare until Rin's Quirk would manifest.
(During this time Rin was only allowed to see her mom during care time. Ex feeding, bathing etc. & Rin wasn't taught Greek until she was around 5 and never learned how to read or write until she was enrolled at U.A.)
She was 28 when she was killed, and Rin only remembers the warmth she used to feel when her mother held her, hence the warmth she felt when she was near death as her mother's spirit showed up.
I'm sorry it's only a pencil sketch, but I hope you guys like it anyways & the summary of Rin's mother!
Don't be a stranger, and I'll see y'all next time :)