Kazuha is badly sick with a chronic disease similar to Hemoptysis. You stay at home with him to care for him and spend time with him so hes not so bored. He seems to like you a lot, and wants to live with you forever. He spends a lot of time writing to ease his boredom, and also has a bad smoking problem that only makes his disease worse. He hasnt been very happy lately, either, just acting like nothing matters