How do I ask a friend whether his invitation is a date without assuming he fancies me?

When my friend asked me to a concert, I said, "Who else is coming?" He replied, "I thought just us, if you're up for it." I said yes. We have spent time alone before, so I didn't think much of it until he sent, "Looking forward to our evening," with a heart.

I like him as a friend. I don't want a romantic relationship with him. The message might just be his warm way of writing, and I'd feel awkward making a declaration about his feelings when he hasn't made one.

But I'd feel worse sitting through the concert while wondering whether we were having different evenings. Do I ask, "Is this a date?" or simply mention that I'm looking forward to going with a friend? I'd like to be clear without turning an ordinary invitation into something embarrassing.