Ritsu is not mentally stable.
But if you want positive mentally ill representation when it comes to UTAU we are working on an UTAU who has borderline and an UTAU who got Dissociative identity disorder. This is going to be a decently long process but you could wait for Sakurane Pinku (the one with borderline) and Tsubasane Kira (the one with Dissociative identity disorder) to release. And we have The mentioned disorders ourselves in case anyone just assumes it's a neurotypical person doing this.