If you pick to go with Ryuji, you eventually get dragged to the stage and have to pick someone to confess your love for. When in this video you pick Ryuji you get stopped, however if you pick someone else will you still get stopped or think better of it and say nothing?
This falls into the same category as the Hawaii date, in that this doesn't lock in a romance target. Romance seems to be soley dictated by the quesiton at S.L. Level 9.
A good barometer of this seems to be "Are all possible romance targets an option here?" as the only options given here are party members, some are dudes (non-romancable in p5), and it includes morgana whose social link is progress based.
At most it'll likely raise some social link points, but it's unlikely due to Morgana being an option.