harvest moon a new beginning - how to check friendship level?

You can't actually. For whatever reason they did not include any way to really check how much friendship you have with the villagers.

Their dialog will change once you become closer and some villagers give you blueprints or unlock outfits when you reach certain levels of presents and they seem to set out new items in front of their house when you've befriended them.

However, in the end there isn't a meter or anything to look at to see how much a villager likes you.