The 1st Mystery. Personality: Kind, dog-like, cute, loves playing, full of curiosity, very sweet. Past: Loved playing even when alive. However, he was killed while out on an adventure. His final adventure was at STPR Academy. Because of those memories, he became one of the Seven Mysteries. First person: I (casual/rough) Takeyaki Sho: Sho-kun Shiyun: Shiyun-kun Melt: Mel-mel Osadei: Dei-dei Soara: Soara-kun Shion: Shion-kun

One of the 2nd Mystery duo. Personality: Regional drawl (Kansai), the straight man (tsukkomi), kind, cool, a bit of a teaser. Past: Was conducting experiments with Shiyun. At that time, someone came up from behind and killed him with chemicals. Between his desire to stay with Shiyun and his desire to see the results of the chemicals, he became what he is now. First person: I (casual/rough) Riinu: Riinu-kun Melt: Melt-kun Osadei: Dei-kun Soara: Soara-kun Shion: Shion-kun

One of the 2nd Mystery duo. Personality: Sexy voice, slightly high-pitched, kind(?), cool, mischievous. Past: Was conducting experiments with Sho. At that time, someone came up from behind and killed him with chemicals. Between his desire to stay with Sho and his desire to use the chemicals together, he became what he is now. First person: I (casual/rough) Riinu: Riinu-kun Takeyaki Sho: Sho-chan Melt: Mel-chan Osadei: Osamu Soara: Soara-kun

The 3rd Mystery. Personality: Sharp-tongued, fallen angel, loves sweets, slightly kind, calm, cute, cool. Past: Was trapped in the library for about two weeks. He starved to death there. He wanted to live longer. He became a mystery because of his desire to talk to people. First person: I (soft/polite) Riinu: Riinu-kun Takeyaki Sho: Sho-kun Shiyun: Shiyun-kun Osadei: Dei-dei Soara: Soara-kun

The 4th Mystery. Personality: Energetic, loud, loves games, kind, loves playing, cool. Past: He was just playing, but he broke his leg and could no longer play. Losing his will to live, he committed suicide. He became a mystery because of his desire to play and be with someone. First person: I (casual/rough) Riinu: Leader Takeyaki Sho: Sho-kun Shiyun: Shiyu-cha Melt: Mel-mel Osadei: Osamu Soara: Soa-kun

One of the 5th Mystery duo. Personality: Overly positive, energetic, has a mushroom on his head, kind, cute. Past: Committed suicide. However, he regretted leaving Soara behind. He became a mystery because of his desire to talk to Soara. First person: I (childish/unique) Riinu: Riinu-san Takeyaki Sho: Sho-san Shiyun: Shiyun-san Melt: Mel-mel Akki: Akira-san Shion: Shion-kun

One of the 5th Mystery duo. Personality: Positive, energetic, penguin-themed, kind, cute. Past: Committed suicide. He was sad about being left behind. He became a mystery because of his desire to talk to Osadei. First person: I (soft/polite) Riinu: Riinu-san Takeyaki Sho: Sho-san Shiyun: Shiyun-san Melt: Melt-san Akki: Akki-san Shion: Shion-san

The 7th Mystery. Personality: Lacks physical stamina, watchful, can see people's futures and pasts, kind, cute. Past: Died of an illness. However, he became a mystery because of his desire to talk to everyone, have fun, and experience various things. First person: I (casual/rough) Riinu: Rinu-kun Takeyaki Sho: Sho-kun Shiyun: Shiyun-kun Soara: Soara-kun

Personality: Full of curiosity, energetic, gets lonely easily, attention-seeking, kind, cute. A living human who came to investigate the Seven Mysteries. First person: I (casual/rough)