You'll learn about some aspect of Japanese culture the more you watch it-- the fundoshi is a part of that culture. From festivals to swimwear, it's important in Japan, but mainly is used as underwear for men. Anime manages to take said underwear and do some different things to it. Here's 10 characters in anime that wear fundoshi -- and no, it's not all guys!
Clain Necran from Fractale
A lot of people will choose to remember Hiroki Azuma's Fractale for better or worse. Now you'll get to remember it as the series that had Clain wearing a fundoshi in a world where that's considered dated.
Shigure Kousaka from Shijou Saikyou no Deshi Kenichi (History's Strongest Disciple Kenichi)
Shijou Saikyou no Deshi Kenichi has a lot of fighters, which means lots of people are getting beat up and beat down. Shigure happens to be one character, but she just happens to wear a fundoshi and is proud of that.
Isao Kondou from Gintama
...Speaking of statements, Gintama is very heavy on Japanese culture, but this is probably not Kondou's finest moment. Well, out of everything he's done in the series, this might not be his worst moment.
Hibachi from Mushibugyou
Hibachi is a ninja who has bombs and uses them well. She also seems to like wearing fundoshi, and that might be due to her family's style and upbringing.
Pesche Guatiche from Bleach
Fundoshi are traditionally white, but there are different colors as you've seen so far.
Tsuruko Aoyama from Love Hina
Motoko's older sister, Tsuruko is very traditional, from her actions to how she dresses. And yes, this is very traditional for her family.
Goemon Ishikawa XIII from Lupin The Third
Needless to say, it would have been difficult to have a list of characters wearing fundoshi and not have the legendary (in history and in Lupin) swordsman Goemon Ishikawa. When he's not cutting everything down with his sword, he's finding a way to take off his clothes and show his stuff. And he's very proud of it.
Matabei Gotou from Hyakka Ryouran: Samurai Girls
This is a very different samurai version of Gotou. In Samurai Girls, we have fundoshi wearing Matabei Gotou, who may be quiet but that spear's something to not be messed with.
Izumi from Queen's Blade Rebellion
We've all heard of Queen's Blade its desire to have women in lots of compromising designs. Izumi just so happens to be one character who's definitely doing her best to wear the fundoshi with some pride.
Satoshi Isshiki from Shokugeki no Souma
Finally, if you've been reading or have watched Shokugeki no Souma, it would be weird to have the 7th Seat in the Elite Ten missing from this list. Mainly because he makes every effort to get your attention. And I mean every effort!
So, anime has taken liberties once again, with seemingly no abandon -- expect that to continue as more shows arrive, with more boys and girls wearing fundoshi.