It's hard to top incest when it comes to bad romance concepts in manga. I've covered a few examples so far, and they've all been awkward and disappointing. Today's selection is a bit different. It's one of the most literal riffs on the idea, and yet it's also one of most satirical and inspired takes.
I DON'T LIKE YOU AT ALL, BIG BROTHER! (Oniichan no Koto Nanka Zenzen Suki Janain Dakara ne-!!), by Kouchi Kusano. First published in 2008 and first published in North America in 2012.
PLOT:
Nao is a 12-year-old girl who loves her big brother Shuusuke. She loves him so much that she's determined to make him her lover by any means necessary. She'll stage "accidential" flashings, throw out any porn of his that isn't imouto-themed, and tries her hardest to turn her bland brother into a sister-loving pervert. The only thing that threatens to get in her way is Shuusuke's old childhood friend Iroha. She took a childhood promise made during a game of Doctor far too seriously and now has her own equally aggressive plans for him. Now the two are locked in passive-aggressive battle for Shuusuke's affections, and only one can win.