Just for a clearer story from what I got after reading through the Japanese chat screenshots and the NHK articles linked throughout the thread. Will roughly convert to USD.
In screenshots of them chatting on Line(chat app) she asked to borrow money from him with reasons like: she forgot her wallet at a part time job but happened to have a cash card laying at home he can send to, low on cash after gifting $1k bottle of champagne to someone important in her cabaret bar group. To add he also alleges in a chat to a 3rd party that she would also have reasons like: her sister has a debt to a host and was in danger of being sex trafficked, she might have cancer or she ran away from home needs money to rent a place, in 3 month intervals, admits he was stupid for falling for these.
He was chasing $25k(there is an image of a document with this amount stated) that she asked to borrow from him through Line messages since late 2023. January 2024 he calls the prefectures police headquarters to inquire about what to do about money that hasn't been returned by an acquaintance, after he had filed a lawsuit the prior year which failed due to her being unlocatable/uncontactable(by prosecutors?) told him to talk to a lawyer or the court.(From NHK article) Lastly asks in end of January-February for repayment, she initially asks for a 2 day extension misses it, he then asks multiple times in multiple day intervals till the 16th for repayment(not clear if 24 or 25) she only replies once(5th) when he asks if she has no intention of repaying him, she denies.
He is 42 allegedly Schizophrenic. Claims he initially only meant to threaten for the money and apparently took out a personal Loan to fund some of this. Not condoning him killing her just providing context that seems fairly verified and justify the time I just spent reading all this.
edit: He first saw her stream in December 2021 and first met her irl in august 2022 when he started visiting the cabaret bar she worked at. Loaning occurred September-December for money to rent a place and living expenses(calls into question his messages to the 3rd party), law suit made August 2023, December it went through that she would be ordered to pay.
He somehow found out she would be streaming along the yamamoto railway line, arrived in tokyo that morning and stream sniped her. ( all from the nhk article.)