But now, one day before she competes in the Dubai Tennis Championships at the Aviation Club Tennis Centre in Dubai, Osaka has brought clarity to the issue and it's all to do with her happiness.
"Everyone thinks it was a money-related issue, but it wasn't," she told the WTA . "For me, that's one of the most hurtful things I've ever heard. I travel with everyone on my team, I see them more than my family. I would never do that to them."
Osaka linked up with Bajin when she was ranked 68th in the world, and the coach guided her to world number one status with two Grand Slam title wins en route. Though she has terminated the relationship, she refuses to "say anything bad" because she remains "grateful for all the things he's done."
Osaka added that her happiness trumps the money as well as the trophies. "The biggest thing is I don't want myself to think to be successful I have to put success over happiness, because if I'm not happy being around certain people I'm not going to torture myself.
"I'd rather just surround myself with people that I really like and that truly care about me and are just really positive. I think I've been able to do that."
She added: "If I'm not waking up every day happy to practice and happy to be around the people I'm around, this is my life. I'm not going to sacrifice that just to keep a person around. I have to be happy with where I am at my life."
Osaka plays tomorrow for the first time since winning the Australian Open in January, and for the first time since splitting from Bajin. This means she has no tennis coach, currently, but has a fitness coach called Abdul Sillah, a physiotherapist called Kristy Starr, and the Japan Tennis Federation coach Masashi Yoshikawa.
Osaka will be expected to beat Kristina Mladenovic in their Round of 32 match with or without a head coach at courtside, but will be without a main tennis trainer for the entire tournament. This is only temporary as she hopes to employ Bajin's successor ahead of the Indian Wells Masters in California on March 4.
But any coach who ends up working with Osaka will have to be encouraging and positive. "I don't want someone that's in the box saying negative stuff," she said. "That would be the worst."
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