#1 The steady decline towards weird sex
Muromi-san is an anime that doesn’t seem immediately off on the surface. It’s about a boy who loves fishing, but who is constantly harassed by the mermaid girl he once reeled in. While he tries to just enjoy his day of fishing, the mermaid Muromi keeps dragging him into weird adventures and introduces him to all of her friends, which are often mythological monsters who turn out to actually be friendly anime girls.

However, there is a downward spiral throughout the show. Early episodes toss in some sexual gags, starting with a bit where Muromi expresses joy at being stung by jellyfish for extended periods of time. It has some peaks of weirdness spread throughout, but the decline hits rock bottom when the show starts giving significant screentime to Fuji—a large-breasted mermaid that has a crush on Muromi.
Fuji has, however, gotten on Muromi’s bad side and frequently frustrates her so much that Muromi assaults her. She’ll tear at her breasts, stab them with sea urchins, or otherwise try to significantly hurt her, all of which Fuji actually derives sexual pleasure from. The show will dedicate several minutes at a time to scenes of their fights and Fuji’s build-up to orgasm. While there is no actual nudity, scenes with her will have her sweating and moaning, her nipples go hard and she becomes increasingly twitchy, it’s bizarre to see in a show that has no age gate whatsoever.
#2 Questionable romance
It’s not just the sexually explicit content that makes this show hard to watch, because it’s also unpleasant and uncomfortable just in general way. Muromi is a belligerent and short-tempered idiot who assaults whatever she doesn’t like and just never shuts up about anything. After she is one day fished up by Takkun, she immediately falls in love and demands he fertilizes her eggs, even though she is an immortal sea creature and he is underage.

I made a similar point in my Kaguya review, but it’s much more prevalent here. The romance between Muromi and Takkun only appears to exist because the plot demands it. It feels like turning over 2 pages at once in a book. Muromi never really identifies how Takkun interests her or why she hasn’t fallen in love with any other human she has met across all of history. Takkun gives her the cold shoulder for much of the first half for comedic effect, but when he is challenged on it suddenly switches and reveals he is just being coy about his love for her.
There is no progress or chemistry to the romance and neither party makes for an engaging character; it’s just kind of there to string jokes together and I call the biology behind fertilizing Muromi’s eggs into question as well.
#3 Consistently unfunny
As a final point, I just have to say that the comedy in this anime deserves to be put between air quotes. This is always a troubling argument because comedy is subjective, but it’s also pretty damning to a show that attempts to sell itself on the basis of its comedy.

For much of the show, I was either just entirely unamused or the joke was so embarrassing that I skipped ahead. To give some examples:
- An alien harassingly interrogates an ambiguous character about whether they are a “shota” or a “loli” and demands they put on a tail and strike an erotic pose.
- The harpy character suddenly has all her dialogue changed into memes and internet language.
- A scene of several minutes where Muromi just rants about why she hates dolphins to an aquarium employee.
- Muromi and other fantasy characters get stoned eating poisonous mushrooms for no reason.
I could go on, but the point is that none of it lands. Both because I felt 0 connection to any of the characters and also because all the jokes are awkwardly presented. Every phase of the gags they pull is lingered on for too long and some jokes, like Muromi ranting about dolphins, don’t have punch-lines at all.
It’s hard to put into words why comedy doesn’t work, so let me just end this by saying that I have never watched an anime that left me as uncomfortable, unamused, and annoyed as Muromi-san.
Yeah when I saw the PVs for this going around I knew it would be a waste of my time so I ignored it lol. Your posts made me realise that was definitely not a mistake.