Just Bento

For me, both liquids are quite different (like comparing a sweet sherry with a dryish vermouth) and both have their own distinctive aromas/tastes.

But when cooking, the simplest way for me to describe why I might use both is that Mirin gives a very distinct kind of sweetness to the dish. Sometimes that sweetness can be a bit cloying. Whereas Sake (and I only use dry or semi-dry sake for cooking) somehow balances the Mirin.

My opinion comes from having used Mirin and soy sauce together with and without Sake. Although Mirin and soy sauce tastes fine as a combination, there's definitely an improvement when a drop of sake is added also. For me, the tase becomes more refined/sophisticated - it's as if Sake becomes a mediator between the saltiness of the soy sauce and the heady sweetness of the Mirin and they all harmonise together.

In teriaki type recipes which provide a salty/sweet flavour you could probably get away without adding Sake if you don't have any. It won't be quite the same but it won't be too far off. Using Sake but not the Mirin won't approximate the intended result (although you could perhaps get nearer by adding sugar/honey/maple syrup).

Wow, I can't say it any better than Loretta has!

There are just too many sake at the store. Different kinds too. Which one should I get for cooking?

Just get one that is affordable for you, that will be fine.

Thank you so much!