2021 New Year – Rebirth of Shiramochi-ō

2021 New Year – Rebirth of Shiramochi-ō (2020正月-白餅王降臨-) is a holiday event that occurred in the Great Tomb of Nazarick. It was be released on January 1, 2021 to January 15, 2021.

Background
Momonga who visited the Round Table Room for a meeting, found Albedo, Demiurge, and a mysterious boy relaxing by a kotastsu and was puzzled. Momonga moves on his own to eliminate the "New Year" mood has spread in Nazarick.――Without knowing that this incident has happened a "second time"

Incident
Previously in Fake Nazarick the entity known as Shiramochi-ō is defeated and vanishes restoring the area to its original appearance. On that day, the "New Year" phenomenon that strick Nazarick ended with the White Mochi King's disappearance at Throne Room of Fake Nazarick. It should have been a case close, however at the same time in real Nazarick, on the 10th Floor at where the Throne Room is, the Crack activates and out appears Shiramochi-ō who announces that he comes at the beginning of the year to purify all the old. His body at the center cracks open and the room is dyed white by the emitted light. From inside something new appears and a young blonde hair youth takes the Ruler of New Year's place. The boy shouts "Kagami biraki" and looking curiously around wonders where he is.

Momonga, who is visiting the Round Table Room for a meeting, finds Albedo and Demiurge dressed in kimonos eating mandarin oranges and warming their feet under a Roundtable that has been converted into a kotatsu. Even more unusual, there is a mysterious pale blonde boy with them. Albedo seeing Momonga present greets him and says "Happy New Year", promising to continue to work hard and make constant efforts for the sake of his supreme self. Momonga is stunned by the revelation that it is already New Year's and that the Overseer Guardian is aware of such a holiday. Momonga decides to get back to the purpose of the meeting but is shocked when Albedo and Demiurge move in favor to skip the meeting and enjoy the holiday. Now worried, Momonga sees that the two are acting out of character and believes that they are under some kind of mental influence. He hopes that the influence does not affect undead, but turns to the more pressing issue as to who the strange boy is. When he asks the two Guardians' on the boy's identity they seem unconcerned replying that he was already in the room when they came. This laxity on their part makes Momonga flag it as a serious emergency as neither Guardian would tolerate a stranger in Nazarick under normal circumstances. Trying to figure out how to handle this, Momonga decides to play along rather intern the child, as he does not want to make the first hostile action. If the boy is involved in their conditions and prompt the Guardians to attack him, it would be bad. Instead he asks the boy who he is. The boy honestly tells him that he does not remember who he is or why he is even in Nazarick. He knows that there must be a reason and so far can only recall that his name is Shiro. As for why he is in the Round Table, the boy states that it seemed to be a very comfortable place to relax in. So far Momonga can tell that the boy is not lying and perhaps that he has been afflicted by a spell like [Control Amnesia]. He cannot discount the possibility the boy was sent to Nazarick for some ill purpose. However the situation in the Round Table needs to be supervised while he goes to figure out what is going on. Momonga uses his magic to summon a Death Knight, passing it off to Albedo and Demiurge as a waiter to serve the two while they enjoy their holiday. The two thank him of his generosity and consideration, promising to work harder next year.

After leaving the two in the Round Table, Momonga in the corridor resolves to investigate and discover what is going on. He first plans to summon several undead to search for any clues to the source of this "abnormality" on each floor. A noise distract and he finds that the boy Shiro has followed him out of the room. Momonga suspicious ask why the child is following him. Shiro states that he wishes to join him in his search for the cause of Nazarick's "abnormality" as it may help him regain his memory. Momonga asks why he would assume that there is anything wrong with Nazarick. Shiro points out several factors like the fact Momonga's subordinates accepted him without any problems and yet Momonga clearly is wary of him and tried to quietly leave him behind. Momonga sees that Shiro is sharper than he gave him credit for. Still it seems Momonga gave too much away when he met Shiro, but he is inclined to believe that having Shiro tag with him may not be so bad as it would allow him to convectively monitor him. Momonga agrees for Shiro to join him on his search as Shiro's missing memories could be connected to this anomaly.

After ordering undead summons to search for any abnormalities, Momonga and Shiro arrive at the 10th Floor in the ruined Throne Room. Momonga asks Shiro if can recall where he first appeared in Nazarick. The boy tells him that all he can remember was saying "Kagami biraki". Momonga hearing the word muses that it has to deal with the New Year. According to Shiro when he first became conscious he found himself in the Throne Room surrounded by skeletons. This draws a question from Momonga, who wonders why the undead summon who were guarding the area did not notify him of Shiro's appearance or maybe they were unable to recognize him as a threat. If that is the case then the mental effect may also affect undead, and Momonga draws the possibility that he himself could be under its influence in some way. Shalltear Bloodfallen appears, greeting Momonga wishing him a New Year. Her comment about the New Year proves to Momonga that she too is affected by whatever is spreading in Nazarick. From her he learns that she is on patrol duty here on 10th Floor. It also seems to Momonga that Shalltear's influence of the New Year's mood is minor as she seems to be dedicated to doing her job unlike the two other Guardians he encountered. Momonga deduces that this could be due to Shalltear being an undead and thus the mental effect is minor.

The new face next to Momonga, draws a question from Shalltear. Momonga explains that Shiro is a "guest" in Nazarick and the two make their introductions. The Crack soon activates pouring out Chaos Beasts as usual but soon more miasma comes spilling out and popping out three monsters that resemble kadomatsus. Shalltear seeing them as enemies steps in to fight, and is joined by Momonga and to his surprise Shiro. The trie easily dispatch the beasts. Momonga wonders aloud what type of monsters those kadomatsus were. Shalltear to his shock is unable to recognize the monsters as anything but Chaos Beasts, not even noticing their appearance as kadomatsus. It also seems that Shalltear is holding something that she explains appeared after defeating the Chaos Beasts. It turns out to be a Biwa, but it seems to have no abilities according to Momonga [Appraisal Magic Item]. Shiro seeing the instrument seems to be familiar with it vaguely.

A Death Knight comes to report that the protagonist and his allies have returned to Nazarick and are on the 1st Floor. The Overlord thinking that those who were outside Nazarick at the time of this phenomenon, believes they may not be affected. Momonga decides to go back to the 1st Floor to welcome the protagonist with Shiro, and tells Shalltear to resume her patrol duties.

Aftermath
TBA