Obligation family- a lesson in Japanese

The other day when I was in Japanese class I was telling a story about my family and needed to know the word for Sister in law. My teacher told me that it was 'Giri no imoto'. I thought to myself for a second that I know the word for sister 'imoto', and I have heard the word 'giri' before- at Valentines day. If you might remember one of my earlier posts 'giri choco' is the obligation chocolate that you have to give co-workers to keep in their good graces. This made me laugh- was it the same word that is used for 'Giri no imoto'?  My Japanese teacher wasn't quite sure, but we have since found out that yes- it is Obligation Sister. Perhaps in Japanese, obligation doesn't have the same negative connotations that it does in English.

At least I can be glad that to me, my in laws are in no way an obligation.