If you're looking for manga similar to Fukugaeru, you might like these titles. All recommendations are made by Anime-Planet users like you!
Tsukimi is an otaku and jellyfish enthusiast whose only means of coping with the world is to reject it: she and her friends live in a house they declare a man-free zone, generally avoid 'stylish people', and spend their days blissfully bonding over geeky rituals. As misfortune would have it, their convenient existence is about to be turned on its head by the arrival of Kuranosuke, a seemingly beautiful young woman who is actually a beautiful young man. While he may be strange even by their standards, Kuranosuke embodies everything Tsukimi secretly dreams of being - a princess as ethereal as a floating jellyfish - and promises the kind of mind-boggling adventures only possible when geek meets chic!
The plot of these two manga are vastly different, but both are about otaku women, who are obsessed with one specific thing, be it jellyfish, ancient chinese literature, or frogs. They feel cut off from normal society, and don't have the best luck with dating, or befriending other women.