Some compelling use of the medium there! Always keeping An's eyes just out of frame.
One possible interpretation is, as
@Ropoloid suggests, that she studied his reaction and was happy to realize he's lying. But the other is that her heart broke, even if just for a moment, and she had to fight back tears. By the time Shunpei finally looks in her eyes, there's no way to tell; even what she said about both of them feeling the same way can be taken multiple ways. He averted his eyes - and because he's the viewpoint character of this chapter,
so did we. Frustrating, isn't it? Shunpei is frustrated with himself, too, I'll bet.
The bus driver is proof positive of the mangaka's mastery of the medium. A character who never says anything, barely even shows any motion, but simply through his strategic placement in key panels towards the end or beginning of the chapter he became enough of a presence in the mind of the readers that when he got a chapter all to himself, no one was confused, and everyone was happy. Never seen more unanimous cheering in discussion threads or comment sections, and I imagine it was no different in its home demographic.
It's no wonder at all other bigshot manga artists are enjoying the hell out of this. Maybe we can dream of a crossover with Masuda Eiji's current work? (Same premise at the core, yet completely different in theme and execution, because it's a crowded train in the city, rather than an empty bus in the countryside. And Masuda is no less a master of his craft.)
EDIT:
Also a favorite moment of mine in this chapter is the very blink-and-you'll-miss-it way An managed to get out of handing the profile page back to Shunpei after filling it out. I don't think there was anything that came after the love corner (this sort of thing is ALWAYS at the end, come on!), so between "she is not done filling it out" and "she does not want Shunpei to see", which is more likely? You may have tricked Shunpei, but I'm onto your feminine wiles! Ha ha ha. I'm so lonely.
Shame we probably won't see Lulu's reaction the next day when she asks for the page back and Shunpei tells her An is going to send it to her by letter.