Would the boy have payed more attention he would have noticed the unmisunderstandable hint that she is not a slut: her shirt with the slogan †žLove is best“!
Ah, some sweet Vanilla goodness, always nice.
"Isn't this a bit sudden?" -> "Love always is"? Yes...Hentai, too, can be quite sudden.
Great ending though. Indeed, love at first sight, and she was just proactive enough to go for it straight away.
What We've Got Here between Lisa and Ryuuji is "... a Failure (or at least a Deficiency) to Communicate." Perhaps a ... wait for it ... continuation of the story will reveal the solution to the situation.