Rainstorm Riddles

So the premise for this sequence of events is that the Swordsmiths are the facility maintenance technicians for the Mermaid Rehab. They fix anything that isn't working right, and aquariums often need a lot of maintenance.

Kotetsu's family was in charge of an old mechanical mer-suit designed to allow a human to swim with merfolk. His parents having passed away, he was put in the care of Mr. Kanamori.

The Haganesuka and Kanamori got called in to do some maintenance on the ceiling for heat and electricity. They brought Kotetsu along with, who wanted to test out the mer suit as he'd been trying to get it back into shape.

With permission and supervision, he was allowed to test run it in the communal tank with some of the friendly and more relaxed mers, AKA Tanjuro, Nezuko, Rengoku, Kanao, and Muichiro. All of which were very curious, but it was Muichiro who didn't have any inhabiting about touching it and, like in the show, he ends up breaking a fin off and making Kotetsu very upset, but doesn't get why he's so upset.

Tanjuro attempts scolding Muichiro, but gives up when all he gets is a blank stare.

Kotetsu spends the rest of the day trying to fix the mer suit, but runs out of time. Still emotional over it, he decides to sneak into the facility after hours to keep working on it.

One of the tools he needs is placed on a ladder leaning against some scaffolding, so Kotetsu makes to 10 year old decision to climb the folded ladder with lots of items leaning against it. The ladder falls and knocks several things down with it, including a bucket of bolts large enough to secure heavy equipment.

As apathetic as Mui is in this AU, AR this point he has been around Tanjuro and managed to regain memories as well as his sense of empathy, so when he sees Kotetsu fall he rushes in to shield him from the equipment.

Muichiro knows that humans can't stay underwater for long, so he drags himself out of his tank to get Kotetsu to the air. All of this happens very fast, so it's not until this point that Kotetsu realized what happened between falling in the water and surfacing.

He sees Muichiro injured from the bolts and beams, and immediately rushes to find help. Once help arrives on the scene, Kotetsu stays with them to help any way he can, which mostly entails pouring water over Mui while Shinobu and Kanae treat his wounds. Kanae recognized that Kotetsu feels very guilty about the situation, which is why she allowed this.

From then on Kotetsu and Muichiro formed an odd friendship. Muichiro did his best to help fix the robot and Kotetsu regularly visits, getting special permission to play with his mermaid friend.