There are crushes, and there are crushes – some you're more likely to act on than others, and some you know are just secret emotions that are better kept to yourself. That last distinction is a little difficult for the heroine of First Love Monster, fifteen-year-old Kaho Nikaidou, though to be fair it isn't entirely her fault. Kaho is the only daughter of a wealthy family, and her older parents have always spoiled and indulged her. They've made it very well known that she's their precious flower, and as a result she's never been able to keep any friends – they either assume she's stuck up or their parents have warned them away from Kaho. In an attempt to end a socially isolating, hurtful phase in her life, Kaho packs up and moves into a swanky boarding house in Tokyo, determined to start anew. Unfortunately, one of the first things she does is almost get hit by a truck. She's rescued by Kanade, a tall, gorgeous boy who asks her if her mother never taught her not to play in the street. She falls for him immediately, and is encouraged in her crush by her new housemate Chiaki. But when she asks Kanade out, he tells her that he'll only do it if she still likes him when she finds out the truth...that he's an exceptionally tall and mature looking fifth grader.

When you look at it from a different perspective, four to five years of age difference isn't a big deal. Then you remember that Kanade is ten or eleven to Kaho's fifteen, and First Love Monster becomes a little harder to stomach, because at those ages, four to five years does make for a huge gap in maturity. Suddenly First Love Monster's comedy is overwhelmed by its creepy factor.

There is no denying that mangaka Akira Hiyoshimaru (predominantly a writer of yaoi) wants this to be a comedy. The visual differences between Kaho and Kanade are amusing, with her being teeny-tiny and him being, to all appearances, a grown man dressed in elementary school outfits, such as a gym uniform, and his name and class embroidered on his underwear. Another denizen of the boarding house, Arashi, is an otaku with a fetish for cute boys dressed as girls, which gets played for laughs fairly well (he invites his girlfriend along on figurine photo shoots in the park), and the way Kanade talks is a fun mixture of childlike and more adult. The issue here is that the romance is played seriously, with Kaho, despite knowing deep down that this is not right, truly considering herself Kanade's girlfriend. She's so desperate for genuine affection that she can't get herself out of what she sees as a real relationship, and there's something disturbing about that.

While the age gap is part of the issue, also upsetting is that Kaho is so emotionally needy and/or broken that she sees this unhealthy relationship as an answer to her problems. She knows it's not necessarily the right thing to do, but Kanade's childish gestures still charm her. The fact that Chiaki encourages the relationship is also troubling, and in fact one of the other tenants gives her grief about it, so there's a sense that the other characters also know that this isn't good. Kouta, a quiet boy Kaho's age who is clearly crushing on her, is the only one who seems likely to object, but he's so shy that he can't bring himself to. All of this adds up to a very uncomfortable read that the continued repetitions of the same basic joke – look, Kanade appears to be a teen but he's really in elementary school! – can't quite cover up.

In some ways, the problem here is that Hiyoshimaru has made Kaho's emotional trauma a little too believable. It's clear that she's really had a tough time of it with her peers, giving her a valid reason to look outside her age group for consolation, and while that would be important in a serious story, in a comedy with this high an uncomfortable factor, it just takes away from the potential humor. Plenty of authors have played the age gap game in romance (in fact, in 2000, Saki Ohta's Yoru Made Matenai followed a similarly aged couple), but something just isn't quite working with this one.

On the bright side, Yen Press' English adaptation is smooth and does an excellent job contrasting Kanade's “my mommy said” speech with his actions and more mature statements, and every character is distinctly drawn in terms of personality so that there is no real overlap, and mostly in terms of art, although Hiyoshimaru's art has some issues with anatomy and the sizes of people's faces seems in continual flux. First Love Monster's brand of comedy, however, is hampered by its damaged heroine and generally mean supporting cast – one new housemate tries to force himself on Kaho, which felt totally unnecessary to the plot, and Chiaki is truly unpleasant – making this much less funny than it could have been.