[M/and possibly also F4F] The Heirs

Main tags: incest, romance, sex-heavy, polyamory, casual sex

Plot

Sai(MC) and his younger sister Sofia(YC, name changeable) are the heirs to a multinational business(United States/Japan). They grew up in the US, and were inseparable throughout childhood, even as teenagers, but once Sai graduated from college, he was put in charge of the Japanese side of the business and moved across the ocean. The responsibilities involved basically took over his life, and he was barely able to even visit home for at least a couple of years, only getting to see Sofia in person a handful of times over that period. But once she graduates as well, Sofia decides to move to Japan to help with the business, and this story picks up with her getting off the plane and getting picked up by a limo to bring her to see his office for the first time.

Extras/Complications

The two siblings were not just close, they were emotionally dependent on each other, something that was discouraged by their strict parents - which was also the reason they never realized they were actually in love when they were younger. On top of that, being separated from Sofia so abruptly combined with the pressure of doing well for the business led to him getting close with his assistant, Yui, and the two have been in a casual, heavily-physical relationship for over a year now.

Sai(refs)

https://gelbooru.com/index.php?page=post&s=view&id=9886181

https://gelbooru.com/index.php?page=post&s=view&id=13971988

https://gelbooru.com/index.php?page=post&s=view&id=14037034

https://gelbooru.com/index.php?page=post&s=view&id=9656185

https://gelbooru.com/index.php?page=post&s=view&id=5755911

https://gelbooru.com/index.php?page=post&s=view&id=5755892

https://gelbooru.com/index.php?page=post&s=view&id=8887097

https://gelbooru.com/index.php?page=post&s=view&id=8374841

Secretary/Assistant Yui(refs)

https://rule34.xxx/index.php?page=post&s=view&id=10179654

https://rule34.xxx/index.php?page=post&s=view&id=7750284

https://rule34.xxx/index.php?page=post&s=view&id=6160991

https://rule34.xxx/index.php?page=post&s=view&id=9263779

Add-ons/modifications

This could all go multiple ways. I would like for this to be heavy on affection and romance, with the two siblings picking up where they left off emotionally but also realizing what their feelings actually mean, and developing physical intimacy as well. At the same time, the situation with Yui will play a factor - Sai isn't shy about the fact that he's been sleeping with her regularly, but does Sofia reject that, causing a hurdle they have to overcome? Or does she accept her brother's casual lover, or even develop feelings for her as well? I would start out playing Yui as well, as a side character, but if there's interest in making her more central to the story, she could be a flex character we both write for, depending on the situation, too. This could also be less slow-burn, and more overtly sexual from the start - Sofia arriving to the office to find her brother free-using Yui in his office, and joining in, for instance, or Sai and Sofia already having a sexual relationship while in high school and college, and reigniting that after so much time separated.