Tsugumi Kokorogi

Tsugumi is Yutori Kokorogi's mother. She is Yuka Katagiri's childhood friend and "knows everything" about her. She was also the one who introduced Yuka to Shiba Taizen who then introduced Yuka to Yuuichi.

It is revealed in Yutori's flashback that Yuuichi orchestrated Tsugumi going into debt most likely the same way he did to Shibe's father. This incurred the wrath of her husband who then started physically abusing her while also turning that rage towards Yutori when her mother disappeared. This shattered Yutori's heart as well as Tsugumi's mind - to the point where she even confused Shinji for being her dead husband, stabbing him as a form of revenge.

She is still in a horrible mental state, distracting herself through alcoholic means while her twisted daughter occasionally berates her for abandoning her. Their relationship is a mix of familiar love, bitter regret, manipulation.