Thank you so much! I'm glad you enjoyed it! ☺️
I won't go into too much detail (in case I decide to continue their story one day 👀), but I can tell you a bit more about Kien.
He's a character who's very meticulous, knows how people work and can adapt his behavior to suit his goals. He's very protective of his interests - and here Sallie is a strong one - and intense with his feelings. However, there is one personal aspect that sets him apart from the general tendency of Yandere characters - he won't willingly engage in physical violence. He knows how to fight (because of his past *cough*), but it's not his thing.