The novel starts with full blast sexual imouto energy as the main character is woken up and kissed by his naked imouto. Then after he wakes up and washes his face in her bathwater, he grabs her bra and uses it as a towel. The nonchelantness by which this is all described turn it into absurdist comedy. In particular the bra towel is very funny. It keeps getting more absurd and zany to the point where one quickly realizes this is just a story being written by the novelist main character of the story.
And indeed, the next scene shows us Itsuki, the real mc of the story, and his editor.
But the presentation of the main story itself feels very uninspired and dull. Unlike the story within the story, which starts out fun and entertaining.
The scene plays sort of plays out like a manzai routine, with the editor is doing tsukkomi (straight man) against the boke (fool) that is Itsuki's script we just read. Itsuki protests against this in a way that serves to keep the conversation going, but doesn't really have him say anything. It feels like we are basically given the template for how such a scene would typically be displayed, without any creative direction given to it. The next scene which introduces a new character is hardly any better.
Chapter 2 then starts with a couple of lines dry infodump on the furtniture in Itsuki's room. There is an accompanying map of the room as one of the insert pictures in the novel. Which suggests that this is not padding, the writer probably put some thought into the atmosphere that the characters live in. And yes, it can be nice to convey this information to the reader since it can add extra flavor to the story. But it should be done in a way that actually builds atmosphere, and not as a dry listing of items in the room.
It was very upsetting to see the funny start turn into such blandness. That is not to say that the whole story should be like the start. The start is way too zany and over the top for that. But the idea of having fun with the presentation is something that is heavily present at the start but completely missing in the scenes following it.