Shougo's father headed a powerful conglomerate before passing away. In his will he states Shougo should inherit the family company, but requires he marries before graduating high school. Shougo transfers to a new school and is popular among female classmates, but there's a problem. Shougo has a half sister who's identity remains hidden. She notified him of her existence at his fathers funeral, and contacts him again saying attends the school as well and intends to marry him. Of the many girls who seems suitable, could he wed his sister by mistake?
Even by standards of harem anime, Nakaimo: My Sister is Among Them is weak. Yet it's the intelligence obliterating story which makes this so annoying it becomes painful.
At first nothing seems critically wrong aside from the usual harem anime antics (lets face it, you're accept those picking this up). The two girls in the lead contending for Shougo's affection aren't too bad. One is a tad generic and the other is a typical tsundere. Arguments over him get old, but that's about it. There's also Ikusu, a girl dressing like a guy working for Shougo's family. She often uses Shougo's shower, then lounges around his apartment naked to "eliminate her scent" which is apparently a ninja thing in a harem warped reality. Other girls are added just to have more of them, and that's where things start going wrong. Harem shows come with a tired set of features (which you may or may not like), putting more pressure on the setup to stay fresh. But holy crap is the setup of Nakaimo idiotic.
Shougo is required to marry a girl before graduating to succeed his father. Would any successful man set his son up to be a victim of gold digger like this? Shougo's sister is among the school students, may intend to marry him. That's the main source of conflict of this anime; a guy may accidentally marry his sister. Really Japan? Really?
Shougo is continually harassed by phone calls using a disguised voice which is incredibly annoying. Why can't the heir of a super huge conglomerate pull some strings to get the call traced? Who knows. That's my big problem with Nakaimo: it bends over backwards to shoehorn this "who's the sister" plot, but it completely fails at logic to make it "work". I doubt an illegitimate child controversy would cause enough scandal to impact a company these days, but I'll let that slide. Shougo confirms a few girls who are certainly not his sister, and later on he's sure his sister must be among a specific group of 5 girls. That means ANY other girl at the school is in the clear. Ikusu could be cleared by his company, says she's fine marrying him, and is already lounging around his apartment (naked). Does it even matter if he marries his sister? She's hidden her identity her whole life, so she could continue to do the same after she married him, and if she didn't tell him he wouldn't know any better. But no, Shougo continues to agonize over the sister stuff counter to logic. Most of this anime is spent toying with the "who's the sister" idea by casting suspicion on various girls.
The harem content is lazy, but amusing at times. The way the girls throw themselves at Shougo is lame, but not unexpected. On those merits it's weak enough, but receives a death blow by the stupid sister stuff. It's not that I didn't know this would involve that, however in this case it's a matter of incredible stupidity approaching the topic.
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