Nudism

Nudism is being naked while doing non-sexual activities socially usually in mix-gender groups whether in a private or public environment for physical and mental health. It is also known as naturism and adamitism. It has been practiced since ancient times by various cultures but the word was first coined by a Belgian named Jean Baptiste Luc Planchon.

Trivia

 * Many Liminals have different morals and levels of shame than humans, so it's normal for them to change their clothes in front of others. However, as Kimihito notes, they often don't realize the discomfort they can cause to others, particularly others of another sex.
 * Some Liminals have very different cultural standards about wearing clothes. In the case of Shapeshifters like Doppel, it is normal for them to be naked, while in turn they are totally embarrassed to wear clothes.