@Yurichan300 Hata no Kokoro is from Touhou 13.5: Hopeless Masquerade, and is the main antagonist from that game.
In general, if you're looking for more information about the many, many, many characters in the Touhou universe, the Touhou Wiki is a really good resource. It's definitely nice to know about the more obscure characters, as they also have pretty interesting backgrounds and personalities.
What bothers me the most about Bowsette is that it's not even the right hair color. I know the power up its based on doesnt really do that, but this is fake anyway, so go the full mile. lol