Hi there! I'm so glad you liked the game so far, your feedback means a lot. As far as the yandere, the game isn't a traditional yandere, however the three main characters (Iris, Seth, The Dust Hunter) are capable of killing their love interest. We used the yandere tag to define this and appeal to people who are interested in darker romance, which is very much Garden of Seif.
*Spoilers below*
There are happy endings, and then there are death endings. Seth may pretend to like you, but he does have an ending where he chooses to kill you.
The Dust Hunter has a killer ending, and there's also an ending where Iris kills him.
Even the killer endings blur the line between enemies and romance, as the love interests (and even the MC) have feelings for the person they are destroying. This is shown the strongest in Seth's killer end.