Also known as: 男水着チャレンジ, 男式泳装挑战
Art challenge where a female character is made to wear Male Swimwear, either Jammers or Swim Trunks, while also topless and in a public space such as a Beach or Pool. Often performed by flat-chested characters, but for tagging purposes, any bust size applies.
While art of girls in male swimwear have been around for quite some time, the first direct response to the challenge appears to have been from November 21, 2020 on Twitter and Pixiv (originally uploaded to Pixiv on the said date).
This tag can only be applied for direct art responses uploaded on Twitter or any art site on or after November 21, 2020. While the "男水着チャレンジ" tag is also being retroactively added to art uploaded prior to the said date on Pixiv, Nico Nico, and the like which appear to follow the concept, it is discouraged to do so here since it is highly likely the retroactive tag additions in said art sites are just mere afterthoughts.