“In-kan” is a personal stamp in Japan. It is used as a signature on documents such as contracts, office documents, and so on.
Usually a last name is printed on an in-kan and it’s easily gotten by anywhere in Japan, though some people use a first name or both last and first name (usually they order personally when making a unique in-kan).
People have two or more in-kan: one (or more) is for a regular use like simple /summary documents, and the other one is for important documents such as a marriage registration and a testament. Normally people buy a regular in-kan at a store like an office goods store but make or order for an important in-kan.