Possible cow from the world of manga- Reiji Miyajima.
While nobody would find any fault with a manga artist drawing his characters and posting them to social media, Miyajima is more than a little obsessed with Chizuru, the heroine of Kanojo, Okarishimasu. If you look through his Twitter account, you'll see that his posts consist of mainly artwork of her, which is a little weird considering there's three other girls in that manga who are supposed to be just as important as her.
What gets really weird is when he started to draw pictures of her in real-life photos he took of his home and other places.
The worst example I could find (that's a picture of his own bathroom):
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Japan is full of weird waifufag schizos, and this normally wouldn't be anything remarkable, but this is not your typical shut-in who will never feel the touch of a woman in his life. This is a near 40 year old, successful artist with a real-life wife and child who is posting his deranged fantasies about
the character he created for all the world to see.
There are so many weirdos on JP art Twitter that they could honestly have their own thread, but never in my life have I seen a successful, world-famous mangaka act like this online.