What should I do if my in-laws don't agree to persuade my boyfriend to break up after Toyoko gets married?

Feelings without parents' blessing will not be happy. Even if you two are stubborn together now, it won't last long because his parents object. It's better to let go of your boyfriend now than to let go at that time. The two of them can get along very well, even if they break up, they can still be good friends. This is the best ending.