Recommendations for an izakaya / cozy fun feel, but for sushi.

Hey all!

Bit of a strange request: I have a sibling in town and we originally wanted to do a sushi omakase, but I’m having trouble judging the vibes of places online. I know some can be very formal, but we’re looking for more casual vibes, still with great chef recommendations. Any recommendations in the Tokyo area? Specifically interested near Ueno if possible.