This is a heartwarming story. The mother-in-law won't die (spoiler), so you have to trust the author! There may be a little angst after the occasional tender moment, but it will have a happy ending. I'm planning to write a coming-of-age story, and the real Kiana will appear.
The protagonist will mostly be on the sidelines in Volume One, while Sirin gets more scenes. The protagonist will have a bigger role starting in Volume Two.
The heroines are tentatively Rita and Sirin. Himeko is also under consideration, along with an incest route. We'll decide on those later.