Lets try this again.

Yori and his twin sister Iku used to be very close as children but lately Yori has grown colder toward Iku and is always eager to stay away from her. Iku was confused by Yori's attitude. Actually Yori is in love with Iku and that forbidden love is causing Yori sleepless nights since Yori and Iku are sharing the same room with bunk beds. Yori tried to ease his intense desire for Iku by bedding Iku's best friend. He had even applied to attend a boarding school in another city to take him far away from Iku. Yori lost his resolve to stay quiet about his feelings when Iku started to talk about having a boyfriend and going on dates. Now Yori want to have his little sister and he confessed. Iku loves her big brother and wanted them to stay together, so Iku is willing to anything to keep them together. But Yori wanted to have Iku as a lover, not as a sister loyal to her twin
Source: ANN

I thought they were gonna pull out "We're not related in blood, LOL" kinda thing, but guess that never happen. When I first decide on watching this, I was hesitant to, because the storyline was near the borderline for me and even went a bit over when they were both in bed. Despite that I continue watching it, taking the incest out, its a good romance story.

Man, I don't remember much in detail but the best part must of been the railroad crossing part. Yori's "gf" got dutched and rejected when Yori and Iku disappeared after the train was gone, I was laughing, "ouch"