I'm just gonna deduct 2 points from Kouhai (saying it's a joke, twice and then running away without letting Senpai finish talking) and 1 point from the Senpai (not speaking clearly. Talking to yourself does nothing to advance your relationship, hurry and cross the finish line, you normie).
Actually annoys me that the mangaka is trying to pass this off as a good resolution to this, with us likely going back to one of the other couples next chapter