But seriously, Mizuki Hitoshi is a guy in real life, so it's presumably just an artifact of anonymization via Touhous.
Irl this still could have happened to him, he left the seat up earlier and then this tired all nighter moment when he need to use the restroom could take place if he needs to take a dump and forgot he himself left the seat up. Poor Kosaga gotta suffer for his mistakes playing the roll of Hitoshi lol.
This has happened to me before. Multiple times. Little brothers suck.
Huh...? I can't get out...Ack!In the Mayhem ③Gyrrk
GyrrkD'hohhh...SshmpI'm beat.... I'm going to the restroom...I'll go in with you.I don't go for that kind of play...What are you doing...?Umph.Saaanaaaeee! Heeeelp meeee...Huh?