Sneaky, manipulative, perverted and very creepy. He is a thief and a voyeur and is willing to stoop very low to get what he wants.
While in human form he has nearly shoulder-length hair, and appears to be always sweating.
When he is in his monster form, he is a giant slug, and can squeeze under doors to spy on girls.
This character is introduced in Volume 2 of the manga, and is only around for one chapter. He mentions having met Kurumu before, when she was competing with Moka for the attention of the male population of the school. She apparently told him that if he took great pictures of her, she would go on a date with him; however, due to how manipulative Nagare has proven to be, this could have been something he made up. When looking through Volume 1, Nagare is nowhere to be found in the background.
He forced Kurumu to go on a date with her by sending her a blackmail letter containing compromising photos of herself showing her underwear. When they met, he revealed that he knew all of her secrets, including her attraction to Tsukune, and threatened to make them public unless she cooperated with him, subsequently forcing her to dress up in multiple costumes (gym clothes, maid outfit, swimsuit, etc.) for pinup photos.
When Kurumu refused to do another session for the sake of helping out the Newspaper Club, Nagare broke into the clubroom and stole the paper's layout and data to ensure her cooperation. Kurumu confronted Nagare at the monster tree, during which he weakened her with poison gas and slipped under the storage room door to confront her. When Kurumu demanded to know how many other girls he had stalked and blackmailed, Nagare simply told her that he hasn't kept count.
At that moment, Tsukune and Moka arrived to help, having found Nagare's first blackmail letter and realized what was going on. Nagare promptly turned his gas on Moka and Tsukune and revealed that he planned to go after Moka next. Enraged at this, Kurumu fought back against him, using illusions to scare and bind Nagare before taking back the layout and data he stole.
AbilitiesEditHe can release a poisonous gas that paralyzes his victims, and can ooze under doors to spy on people, which he does to learn the secrets of girls he stalks, such as Kurumu.
He admits to being good at finding out all a girl's secrets on the 'date' with Kurumu, but it doesn't become apparent what he meant by that until he attacks her at the shed later in the chapter.