Tsunade

Tsunade is a character from Naruto.

Naruto: Ultimate Ninja 3
In the video game Naruto: Ultimate Ninja 3 you can see a cut scene where Tsunade bathes with Naruto in a Hot Spring as part of the Mixed Bathing day that the Hot Springs has. Tsunade seems undisturbed by bathing with Naruto and says that there is nothing wrong with mixed bathing every once in awhile.

Trivia

 * This contradicts the anime since in the anime Tsunade is shown to have her own personal Hot Spring, making it strange that she would bathe in the public one.