O-ohhhh...!? What's this? A new swimsuit?

That's pretty aggressive for you, Tamaki......

Th-this is what they call a ninja fundoshi...

...Um Well, that's not really true......!

This is what one calls a "shinobiki", said to have often been used by ninjas. (It was usually made of white material) It fulfilled the criteria of being "easy to move in", "unable to get snagged", and "not bulky". It has the particular feature of having strings at both ends of the garment. The strings at each end are tied around the neck and the waist respectively to ensure it remains in place, and doesn't flutter around. It's designed not to hinder infiltration missions or battles. It's also possible to use it as a "Etchu-zen" fundoshi, which has a similar shape. Wearing it this way can help conceal one's true identity. In an emergency, it is also said to be able to be used as a bandage to stop bleeding, or as a cord to tie things up.

Ninja Fundoshi Swimsuit