Koohii is a minor character in Crystal Story II, who was a recurring side quest boss in the original Crystal Story. In Crystal Story II, Koohii appears as the secret final boss in Doom Lair. However, unlike in the original Crystal Story, she does not appear in any cut-scenes in the original Crystal Story 2.
According to DeviantART, she seemed to be ticklish. (So is Lina, Mari, Kaeli, Phoebe)
She is given a sidequest chain with cutscenes in the Sword of the Fallen Dragon expansion, reminiscent of the Crystal Story sidequest, where she was deceptively underleveled. She also happens to know Lina back from their Thieve's Guild days, even going so far as to call her a traitor.
For some reason she's taken one of PHOEBE's hammers down to a Beach... I wonder what her next heist will be...