I think the canon skipped over any scenes of Rin and Haru on the way to Australia just because it would've been a NIGHTMARE to try and portray. They'd have to get Haru packed, get him onto the train to Tottori, get him onto a plane to Tokyo, and get him onto ANOTHER plane to Sydney, so for them not to have spoken at all during that time seems unlikely.
However, if they spoke, I doubt it was anything to do with their lives at the moment, by mutual silent agreement. Suggesting grabbing a bite to eat before boarding a plane, offering use of a blanket on the overnight flight, loaning use of an mp3 player (probably full of English songs that Haru would decline)--that kind of idle stuff I can see. Kind of like pointedly ignoring the Big Stuff but still being civil with each other, as suggested.
Re: the tenses, I've had similar issues. It comes up quite a bit when you write long, extended flashbacks, because you're compelled to write in pluperfect to remain explicitly grammatically correct (e.g. "Rin reflected back on their time together and remembered when they had first met. He had been eleven at the time, and Haru had just kicked his ass in the pool." -- lots of 'had', in other words). But when you're writing thousands and thousands of words of that, it's easy to forget you're not writing in simple past.
So writing in the pluperfect, as Lin has done in the excerpt, is correct, because Rin is thinking about action-before-the-present, when 'the present' is already written in the past tense. That tense should be stuck with as long as the flashback is happening (or as long as the character is thinking about things that happened in the past), though I must confess that I've cheated and slipped steadily back into the simple past for extended flashback passages (like All That Glitters).
Re: rinharu week
However, if they spoke, I doubt it was anything to do with their lives at the moment, by mutual silent agreement. Suggesting grabbing a bite to eat before boarding a plane, offering use of a blanket on the overnight flight, loaning use of an mp3 player (probably full of English songs that Haru would decline)--that kind of idle stuff I can see. Kind of like pointedly ignoring the Big Stuff but still being civil with each other, as suggested.
Re: the tenses, I've had similar issues. It comes up quite a bit when you write long, extended flashbacks, because you're compelled to write in pluperfect to remain explicitly grammatically correct (e.g. "Rin reflected back on their time together and remembered when they had first met. He had been eleven at the time, and Haru had just kicked his ass in the pool." -- lots of 'had', in other words). But when you're writing thousands and thousands of words of that, it's easy to forget you're not writing in simple past.
So writing in the pluperfect, as Lin has done in the excerpt, is correct, because Rin is thinking about action-before-the-present, when 'the present' is already written in the past tense. That tense should be stuck with as long as the flashback is happening (or as long as the character is thinking about things that happened in the past), though I must confess that I've cheated and slipped steadily back into the simple past for extended flashback passages (like All That Glitters).
Hope that helps!