The following contains spoilers for Episode 24 of Komi Can't Communicate, "It's Just White Day," now streaming on Netflix.
In more than one way, Komi Can't Communicate by Tomohito Oda is a self-parodying manga and anime. Not only does the manga parody aspects of everyday life in Japan, but it even parodies common tropes found in a lot of anime, manga and light novels. Some of these parodies are found in the puns that make up the characters' names, often describing a character trait they possess. This is strongly the case with series protagonist Hitohito Tadano, whose name in the Japanese name order is a pun on "ordinary person" or "just an average guy."
True to his name, Tadano is often depicted and treated by the other characters -- including his sister and friends -- as unremarkable. He's often ignored at best or a victim of unfortunate circumstances at worst. Arguably, one of Tadano's worst yet most playful critics is his younger sister Hitomi, who often pokes fun at her brother's spinelessness and inability to take initiative in his own relationships. In the Season 2 finale of Komi Can't Communicate, Hitomi makes a comeback, along with another item that seems to be another cruel joke on Tadano: the Gomi-kun wa Gomi Desu manga that Najimi Osana read in Season 1.
Though the cover is not on full display in the Season 2 finale as it was in its debut episode in Season 1, the title of Gomi-kun wa Gomi Desu literally translates to "Gomi-kun is Trash." Though Gomi-kun's name is not written in katakana like the Japanese word for rubbish (gomi), his name is still written with the kanji for "five" and "foolish." This effectively establishes that his name means either "foolish five" or "five times a fool."
In both cases, the title of the manga is conveying that the protagonist is both a fool and a trash human unworthy of respect. This is even conveyed in the manga's tagline, which clarifies that Gomi-kun is a rubbish protagonist. The cover art further drives this point home by depicting Gomi-kun as a high school boy who looks an awful lot like Tadano, only completely covered in rubbish and walking in an alley surrounded by bins. The fact that Hitomi is depicted reading this manga in the room she shares with her brother while he's stressing over what gifts to get his friends Shoko Komi and Makoto Katai is not accidental.
Since the Valentine's Day episode, Hitomi has been aware of her brother's conflicted emotions over the fact he only got chocolates from a boy in his class (Katai), and not from anyone else aside from herself and their mother. What Hitomi doesn't know is that her brother was really brooding over the fact he didn't get any chocolate from Komi, his actual love interest. When she sees him stressing over what gift to give Komi for White Day, Hitomi naturally assumes he's struggling to decide on a gift for Katai and is frustrated by his cowardice.
Deciding to help her "gay" brother come up with a meaningful gift for "the boy in school," Hitomi first suggests that she simply buy him some chocolates or any other food item, as no one will ever turn those down. Tadano, however, thinks he should come up with a more original gift that holds special meaning to the person he wants to give it to. This is when Hitomi tries to get him to acknowledge his feelings for Katai by asking him what he experiences when he thinks of the person he loves. Tadano, of course, thinks of Komi and admits that there might be romantic interest. Taking this as confirmation that her brother is in love with Katai, Hitomi decides to take Tadano to the mall to help him pick out a special gift for the boy.
While the Gomi-kun manga Hitomi is seen reading in Episode 24 doesn't necessarily reflect her opinion on Tadano as a trash human being, at the same time, his inability to do simple things for the people who are most dear to him is a source of frustration for her. Since the protagonist of the Gomi-kun manga is also assumed to be a spineless pushover, in this regard, Tadano does indeed resemble the protagonist.