Tomoka was a friend of the Yuki twins. She has liked Yori for years.

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. 

Tomoko Kawakami was a Japanese voice actress. Having graduated from the Toho Gakuen College of Drama and Music, she was affiliated with Production Baobab at the time of her death.

In August 2008, Kawakami was diagnosed with ovarian cancer, which required surgery. During a three-year battle with cancer, most of her ongoing roles were replaced by other voice actresses, although the latter was able to do some voice work until her retirement in the start of the 2010s decade. She died on June 9, 2011 at the age of 41.

Yori's attitude has changed. He and his twin sister, Iku, used to be inseparable as children, but lately Yori's been different -- eager to be apart from Iku. Iku worries that he hates her, but the truth is far more scandalous. Now, Yori would risk losing everything to have his little sister. Iku loves her big brother enough that she would never risk losing him, and so she'll do what it takes to keep them together... but Yori doesn't want to have her that way -- as a sister dedicated to her twin. Can Iku ever love Yori not as a brother but as a man?<br><br>
(Source: ShoujoMagic)

Tomoka Kusunoki