18-year-old Hime Gotō receives a key to a mysterious and secret building, which is revealed to be a storehouse filled with manga manuscripts written by her father, Kakushi. The current story is set 8 years ago, when Hime was 10 years old. When Hime was born, Kakushi, an ecchi manga writer, vowed never to reveal his job to his daughter for fear of being repulsed by her, going as far as to store his manuscripts faraway, revamp the office building to make it look ordinary, and leave the house in a suit. However, when a new editor Satsuki Tomaruin arrives at the house instead of the office, Kakushi redraws the character on the manga-present T-shirt he is wearing to something unrecognisable.

The end of the year approaches; at G-PRO, Kakushi tasks his team with finishing the proofs for both issues six and seven of their manga ahead of schedule, so as to be able to take time off until January 8th. However, Kakushi himself has no motivation to go through with it. Whilst shopping, Hime wins a hot springs trip to Izu for herself, Kakushi, and Roku, valid from the 6th to the 31st of January; with this newfound motivation, Kakushi manages to finish issue seven. Unfortunately, he catches a cold immediately after, confining him to his futon. All of his friends (including those who think he is romantically interested in them) come to check up on him; in the morning, he feels better and gets up, only to find his room covered in marriage proposals. They leave for Izu shortly after.

At the inn in Izu, Kakushi worries about not being able to keep an eye on Hime in the gender-segregated onsen; he gets Rasuna and Aogu (who he'd bribed with a free trip) to watch her. However, Hime finishes in the onsen before the two even get a chance to enter. Walking back to their room, Kakushi asks an inn attendant about a sealed-off room; she replies that it's being remodelled into a showroom, as it was where a literary classic was written. In the dining room, people spontaneously start telling others about their secrets; Kakushi almost reveals his mangaka career when a scream is heard. Rasuna says she saw a shadow in the room, and the inn attendant admits it's actually haunted by the ghost of the book's author. Later at night, Roku runs into the room, prompting Kakushi to chase him; he discovers that the shadow was actually that of a civet's. Marvelling at the room's history and quietude, he decides to work on his manuscripts, and is mistaken for the ghost by a group of young boys peering in through the window.

In the present, Hime is sitting on the porch of the home-turned-warehouse when a boy her age greets her, and calls her "Sis". He reveals that Kakushi is the love child of a kabuki actor and his mistress. Somewhere else, Satsuki and Rasuna discuss this revelation, and speculate that Hime's maternal grandfather resented Kakushi not because he was a mangaka, but because he was born into a family of kabuki actors. Meanwhile, Naru Senda, now a reporter for the Weekly Bunshio, interviews a worker at the company Kakushi went to work for after he gave up being a mangaka. He reveals that Goto was crushed beneath a stack of mangazines he was moving, because its structural integrity had been damaged - someone had taken out a copy to read. As a result, he's been hospitalised for over a year by the time the series started. Satsuki and Rasuna further discuss how Kakushi's finances had spiralled, not the least because he was searching for his wife. When Hime entered lower secondary school, a tabloid picked up that story, causing him to quit his career.

However, Hime managed to get through upper secondary school just fine, having inherited her art skills from her grandfather. It comes out that the boy's mother, Kakushi's half-sister, was the one who'd sent Hime the key; Kakushi had requested she sell everything inside in order to help Hime survive should anything happen to him. At Tokyo Women's Medical University Hospital, Kakushi suddenly regains consciousness, and Hime and everyone else rush to his side. However, Kakushi doesn't recognise Hime, asking who she is. It turns out that he does retain most of his memories, only losing the past seven years of his life. To him, Hime is still a 10-year-old girl. Kakushi wishes to get back into drawing Tights, not knowing the series had ended years ago, and his former assistants oblige him. Hime sees his father work for the first time. Kakushi asks the now 18-year-old Hime if she's a new assistant, and asks her to keep an eye... on herself.