Don't let the Pizza Hut exterior fool you; this is a decent place to grab a quick, fresh and cheap sushi combo lunch.
Have been a few times with friends and mostly order the Sushi A combo for $8.95, which gets you two maki rolls (generally go with the California and Spicy Tuna), a ginger salad, and an egg roll. The ginger dressing here is quite good, but be sure to ask for it on the side unless you want your lettuce literally drowning in ginger goodness. The veggie egg roll isn't too greasy and the sushi is average but fresh. All this for $8.95 makes it a great lunch deal if you're in the Cotswold area.
A must have if you aren't ordering off of the combo menu is the Cherry Blossom roll. It's the best roll I've had at Koishi and comes out looking like a flower, which gives it a little extra something, in my humble opinion.
Service is a bit on the slow side but generally friendly. And there is plenty of parking on the side and behind the building. Only gripe is that it's tough to get in/leave with the barrier in center of Sharon Amity and the no U-turn signs, but no worries; it's worth the bit of extra maneuvering.