A spin-off of Blue Lock focusing on Seishirou Nagi.

The night of a family birthday party. The mother is tired from work and wants to drink a beer as soon as possible. The father is fidgety and keeps an eye on the clock. A little girl is excited about the sumptuous meal and runs around the house. The intercom rings. There, a new family member is standing there... (Source: Official site, translated)

In the year Universal Century 0079, a state of war began when the Principality of Zeon declared its independence from the Earth Federation government. In the war's opening stages, the Zeon forces maintained an advantage thanks to the effectiveness of their new weapon, the mobile suit. However, they lacked the fighting strength to fully conquer Earth, and the war became a stalemate. Eleven months after the outbreak of war, a base in Zeon-occupied Eastern Europe is captured by the Federation Forces. A Zeon composite battalion is sent to recapture the base, and among its members are Solari and her Red Wolf Squadron, a mobile suit team that has only just arrived from space... (Source: Official Website)

After waking up in her room on Christmas Eve, high school student Ryouka Tsurumi makes a series of chilling discoveries. Her mother informs her that her mansion has been evacuated and the area placed on lockdown due to the presence of an unknown and dangerous entity named X. The only other person left in the building is Shuuhei Murosaka, Ryouka's childhood friend. To add to the horror, Ryouka learns that X can brainwash people for its gruesome goal: feeding itself of human blood to reproduce. However, Shuuhei comes to Ryouka's rescue and manages to save her from one of X's brutal attacks. As the two friends try to escape from the lockdown area, they are captured by hypnotized humans and subsequently devoured by the giant beast. But for Ryouka, the nightmare has just started: she wakes up for the second time in her room, only to find out that a different X is now threatening her life. Realizing that she is stuck in a time loop, Ryouka decides to team up with Shuuhei to find a safe future away from the threat of X.