Japanese curry is peak savory food. Nothing like Indian or Thai curries at all, very much its own thing. Not usually spicy at all, but can be if you want.

Sort of between a sauce and a stew. Sometimes with veggies in it, sometimes just a homogenous thick delicious stuff. Goes great over rice, and especially with breaded things like tofu or, if you eat meat, chicken or pork. The curry sticks to the breading and, fuck, my mouth is watering just typing this up.

If you’re curious, see if any Japanese restaurants near you make Japanese curry, or try the grocery store roux boxes like in the OP. Basically just cook down some onions and add the roux with water, carrots, and potatoes and then simmer for a bit. Can add whatever else you’d like, tho carrots and potatoes go really well with it.