Take a large underpowered amphibious tracked carrier, add a pair of torpedoes (making them dangerously top-heavy and unstable), strap two of them to the deck of a submarine, surface outside the enemy's lagoon harbour, take quite a while to prepare for launch, release the carriers and attack the ships in the lagoon!
Anyway, the Ka-Tsu is a most unusual subject, and we have Riich Models (yes two i's) to thank for a quite nice 1/72 scale kit of it After a five-day build here's what I ended up with. My build log with images of modifications and scratch-built details is over on the Missing Lynx Braille Scale DG: https://www.tapatalk.com/groups/missinglynx/viewtopic.php?f=47210&t=316081&p=1531131#p1531131
Thanks for looking.