Is reading a book that includes a love story between a man and a man, in a foreign country and for study purposes, forbidden and earns sins, knowing that it does not support homosexuals and their actions?

It is not permissible to read books that promote perversion, even for study purposes, because perversion is one of the greatest abominations, and Islamic law came to block the means to evil.

One must beware of the devil's steps and request that this book be replaced with an acceptable book from the school or its administration. If they refuse, do not participate in reading the story unless you fear clear harm. In that case, you participate to the minimum extent necessary to avert the harm, while detesting the story. There is no sin upon you in this situation, for Allah does not burden a soul beyond its capacity.