Considered as a national legend, the 47 Ronin story is all about honor, duty and all that the Bushido stands for. Sengaku-ji is a small temple in the middle of a quiet neighborhood. Easy to miss if you don't know what are you looking for and really beautiful to visit.
Shinagawa station is one of the biggest train hubs in Tokyo, but if you ask me, I prefer to step out of the station itself and wander around the area. There are lots of interesting spots close enough that are worth the visit.