(Dummy me thinking where your response went and didn't see page 2 -_-)

"Cut it out," he snapped.

"Where. Is. Frank?"

"He rarely answers," he replied.  "At least he rarely answers me.  I figured you would know where he is since the two of you have...gotten closer the past few months."

"I wouldn't know either," Rai goes, essentially denying the "gotten closer" thing. "I just check in once in a while. Without him knowing." He adds, "Not to sound suspicious."
We all know you can be a creepy but well-intentioned stalker, Rai. It's fine.
Smirkster doesn't think it's fine, though. Ah well.

"Hint: He's probably at school right now, unless he went astray," Rai informs logically, seeing as "today" is a week day. Or the narrator's stupid as heck, which is probably the case. "And I was about to ask you that, seeing as minutes of your precious break time are ticking away as I speak."

"Hmm, the first one's a hard one, but for the second question, I want to eat food, indeed," goes Rai ironically. 

"Here? You sure this is even the right city? Plus, following you on a motorcycle seems awfully inefficient. In the opposite case, do you even have two helmets?" he asks skeptically.

"And? What about the two other questions?"

"He ditched school?"

On his part, Rai looks about as incredulous as he can look. 

"Yeaahh...probably not." Rai turns around a bit as he yawns and then doesn't turn back once he's finished. "Can't go back to Rayani without blowing my cover right now, if you know what I mean. And there's not enough time, anyways. You need to go eat. Same with me." He raises his arm up a bit, maybe to check his watch? It's hard to tell from where Quinn is. "Both of us need to get back to work soon."

"But I need to eat," he points out, seemingly with zero intent in making the conversation any more tolerable. 

Well yeah, but if he doesn't eat in this verse, he's gonna die from starvation.
Rai waves in Shinya fashion--seemingly sarcastic, way too cheerful, to the departing Quinn. It's supposed to mean "Have a nice lunch! Bye!", which is not something Rai expresses himself.
Frank gets the automated message, "Shouldn't you be in school?" which is always on unless Rai turns off the function...which was delayed because Quinn kept him from taking out his phone and stuff. Ordinarily, he would have switched that message off when lunch hours came. Anyways, his phone doesn't ring, since he also has that muted on default...good job, Quinn.

It isn't instinct that makes Rai take out his phone. Instead, it's him wanting to text Quinn a "" for later. And after he opens his phone, which is a heck of a lot harder to open than usual phones, he sees the calls. 
By the time he sees, though, Frank has already hung up. Speak of the devil, he thinks as he starts to call Frank back. He stops, though, and instead powers off his car first. Keeping the car open during a phone call is stupid. And then he corrects "the devil" in his thoughts to "the birthday boy," in case inauspicious things happen if he thinks of a birthday boy as a devil. And then he calls back.

Well, it just so happens that the usual saying is "the devil" in English. If Rai thought in Chinese, it would've been "Cao Cao"...who happens to be someone who's pretty devilish, actually, not matter how talented he was. Ah well.
"Someone was bothering me. Change of pace. What's up?"