First Day (入門初日, Nyūmon Shonichi) is a manga-omake included in Volume 11.
Sagiri and Shion (佐切と士遠, Sagiri to Shion)[]
At age 2, Sagiri meets Shion who has just joined the Yamada clan and becomes disturbed by the scars on his eyes. To make her feel at ease, Shion makes a face that causes Sagiri to laugh. In the present, Shion reflects with Fuchi on how the first time he met Sagiri was when he came to realize his knack for comedy and proceeds to make a face for Sagiri who laughs in response, believing that not much has changed.
Sagiri and Shugen (佐切と殊現, Sagiri to Shugen)[]
At age 4, Sagiri meets Shugen, who is planning on chipping his sword with a rock, and asks him many questions about his appearance and behavior, which leaves him speechless. In the present, Shugen talks with Sagiri on their first meeting and reflects how it leaned towards the fundamentals questions one may ask about themselves. However, Sagiri corrected him saying that her first time meeting with him was simply a matter of curiosity.
Sagiri and Fuchi and Senta (佐切と付知と仙汰, Sagiri to Fuchi to Senta)[]
At age 6, Sagiri tries welcoming Fuchi after he joins the Yamada clan but is brushed off after the latter states that he only joined for work. In the present, Sagiri talks to Fuchi about the first time they met and states how she found him to be prickly at the time, only for Fuchi to tell her that he doesn't quite remember. Senta then asks Sagiri about what she thought of him when they first met. After remembering how they both nervously stumbled over their words interacting with each other, Sagiri tells Senta that she felt a similarity between the two of them at the time.
Sagiri, Kishō, Genji, and Isuzu (佐切と期聖と源嗣と威鈴, Sagiri to Kishō to Genji to Isuzu)[]
At age 9, Sagiri meets Kishō who joins with a declaration to have his name known throughout the eight provinces. Sagiri then meets Genji who expresses his gratitude for taking him and his sister and introduces himself. Sagiri then meets Isuzu who apologizes her brother's behavior and receives a compliment on how beautiful her skin is. In the present, Sagiri looks at the three and reflects on how they have not changed since then.
Sagiri and Tenza (佐切と典坐, Sagiri to Tenza)[]
At age 12, Sagiri welcomes Tenza after he joins the Yamada clan but is pushed aside as the young man states his refusal to be welcomed by a girl, which leads to Shion reprimanding him for his behavior. In the present, Tenza apologizes to Sagiri for acting rudely to her at the time but is told by her that she did not mind. Tenza then thinks back to how he really felt at the time, having secretly been flustered meeting a girl for the first time.
Sagiri and Jikka (佐切と十禾, Sagiri to Jikka)[]
Sagiri finds it hard to remember the time she first met Jikka but recalls that she was 13 at the time. On the other hand, Eizen, Genji, Shion, and Fuchi have different recollections of Jikka's first day; either that he was drunk, he had beheaded 20 people, he had performed a handstand while in the nude, or he had floated in the air. A drunk Jikka recalls his first day being amazing but realizes that he was referring to the view of a mountaintop he was on, leaving the recollection of his first day unknown as he states that he does not remember.