He's Pretty Tough! Be Careful Susumu!

He's Pretty Tough! Be Careful Susumu! (彼はかなり厳しい！注意してくださいススム！) is a background song Mr. Driller Drill Spirits. It is played during the fight in the Prismriver Circus.

In the anime
When Susumu tries to find a seat at the Prismriver Circus, he finds that there are no open seats. Upon informing the staff, they prep him a special seat using his design. When the show begins, Susumu learns the show host is actually Keel Sark and launches Susumu on-stage. The entire performance ends up turning into a martial arts tournament where the stage is used as the arena.

When the fight begins, three cosplayers cosplaying as the Prismriver Sisters end up playing the song on their electric keyboard, violin, and trumpet.