Shinigami-sama

School Mystery No.6 is a supernatural haunting Kamome Gakuen on awaiting the moon, a day where several come together to weave baskets without succumbing to sleep. He is currently known as The Reaper from the rumors and guards the boundary closest to the Far Shore. However, he can only appear once each year for this event.

According to Chapter 67, it was later revealed that he was the caretaker of Sumire when they were younger.

Appearance
His initial appearance when meeting Nene and Akane portrayed him as a tall figure with immersurable strength. He has furry arms with sharp fingernails, and he wears a mask similar to a goat's skeletal head (with two small horns protruding upwards and two others curling to the sides). It contrasts with his supposed appearance from the rumor, where he is seen as a giant skeleton being.

While he and Aoi are riding a gondola, he finally reveals his face after taking his mask off. He has a human-like appearance, with fair, dark skin and short, scruffy hair. There are thin lines drawn below his eyes; in addition to him possessing pointy ears and curling horns.

In the past, his appearance wasn't much different from how he is now, other than his height and the clothes he wore. He wore a simple, white kimono decorated with beads and tassels, and seldom wore his mask around Sumire.

Personality
According to the meeting with the other existing School Mysteries, Kako states that No.6 may take extreme measures, when they were configuring a solution to deal with the feral supernaturals seeking a seat as School Wonder.

He holds a great sense of duty while disregarding others' opinions, evidently shown as he kidnaps Aoi but promptly apologizes after disappearing. He is seen to have polite mannerisms but occasionally makes blunt statements, such as his wanting to eat Nene and Akane.

After kidnapping Aoi and taking her to his Boundary, he attempts to make amends under a gentle facade, but failed to do so when the flower wilted in his hold.

From Chapter 67, he shares a history with Sumire, stating that he was her caretaker due to his master's orders. He rarely shows many emotions aside from seriousness, stunned, or remorse, especially when Sumire noticed his look of indifference when they were preparing her for the sacrifice. When Sumire was awakened as his supposed yorishiro to repeat the events of her wedding ritual, she said that No. 6 has never visited her once.

Strength
After releasing Akane and Nene from his grip, he mercilessly kills his supposed subordinates after they claimed to be seeking prey for No.6. He also rebounds quickly after Akane's attack when he used Time Stop, slamming Akane's head to the ground when he became distracted with Aoi.

Withering
As the God of Death, living things are susceptible to wilt or weaken under his touch. As he kidnaps Aoi and carries her to his Boundary, she falls unconscious within his hold, waking up to find herself in a boat in the next scene.

Luring
According to the rumor, sixth of the School Wonders will play the flute, signaling when someone is close to their death. Nene becomes frightened, having been reminded of her close death's day when she hears the sound of the flute while they were prepping for camp. For those who heard the flute, they were susceptible to being taken away by the Reaper when they fell asleep, prompting others to protect them by not sleeping.

Subordinates
The assistants of No.6 are small yokai(s) with flowers budding on top of their heads. He can partly understand them through charades, and he tasked them with surveying the school's occurrences and preparing the Kannagi (the one chosen for the sacrifice). He believes that by offering the kannagi's soul and blood, he can prevent the rogue supernaturals from entering by blocking the Boundary connecting the Far and Near Shore.

Resurrecting
According to Natsuhiko, No. 6 can bring the dead back to life.

Trivia

 * In Volume 0, A unnamed bird-like apparition had the spot of No.6.
 * In the rumor, he depicted as a Gashadokuro, a giant skeleton yokai who eats humans.