[2yu]

Usually, my bother picks me up after class, but yesterday I had to stay at school to finish the missed test, so I told him that I would call him when I finished. Unfortunately, I got some problems with my phone and couldn't make a phone call or even text message after finishing the test. At that time, my teacher had gone and there were no many people left at school. I was really scared because I've just transferred to this school and still not have friends yet. I walked around, hoped that I could see someone I know to get help. After nearly 30 minutes, I saw a Japanese guy that I talked to several times at school (mostly about my Japanese concern :]). I told him my situation and asked to borrow his phone to call my brother, yet he accidentally left it at home (agruhhh). Then, we decided to walked to his house to call my brother. Right when we got out of the building, he took off his coat and gave it to me 'cause "Its really cold today, you may get a cold." I was extremely surprised and disconcerted, but he kept saying that it was fine to him (:|).
I don't know much about Japanese and stuff, and his English is not good enough to explain whatever he thinks, so… Is it just a common thing that Japanese guys do for their friends? I kept on wondering about that because we haven't been together much or known well about each other.
I know its kinda silly to ask such a question like this, but… what should I do to show him my thankfulness?