haru sounds disappointed, he knows he does, because in the end, he is learning so he can show it to his fans but he’s not improving at the pace he wants to so it’s frustrating. he’s never really played an instrument before so this was all a new experience to him and he wonders if he’s even cut out for it. yuri, on the other hand, does have lots of experience though so maybe…?
“you haven’t tried playing the guitar before, have you?”
yuri doesn't keep up with haru's idol activities, it's too packed for his liking ( is what he'd like to say, but the truth is there are some things he knows, even if yuri doesn't understand. isn't it only normal to support a good friend anyway? ). haru wanting to learn the guitar is news to him, then again the other boy usually somehow manages to surprise him despite their several years of friendship. it's much easier to pick up a new skill these days, with all the online tutorials available and accessible for free. that doesn't make it easy to learn, but haru probably doesn't have the time to look for a suitable teacher.
it's not like he's here to kick haru when he's down, but the idol is no stranger to yuri's hurl of not-so-serious jabs and playful insults, it'd be weird to cut back now. yuri shrugs, a small smile of triumph on his lips. "you know me, i can't lie to you. even if they're white lies." pressing a hand to his chest, yuri lets out a brazen sigh, as if the concept of lying to haru would shatter him—in a way, it probably would, but haru doesn't need to know that. "aren't you glad to have such a good friend like me?" he asks, expecting no answer, simply teasing.
"as i thought, you are trying to woo your fans," yuri nods. "lucky me, being the first to see agito's precious maknae pick up a guitar. i should've recorded it, i'm sure i can get a fair sum of money if i hand it over to dispatch." he's only joking of course, he'd much rather keep such a video to himself. for blackmail purposes. nothing else.
he does notice haru looking a bit down in the dumps, almost like a kicked overgrown puppy. "it's not easy, though. i applaud you for sticking to your own words. learning an instrument can be very complicated. if you keep at it, your efforts won't be in vain." his tone may sound a little harsh, but if anyone can spot the hint of warmth in yuri's reassurance, it's haru. "don't beat yourself up too much, that's my job, isn't it?" yuri won't take no for an answer.
a part of yuri wanted to tell haru that no, he hadn't played the guitar before, but that would be lying too. he remembers his father handing him a guitar too, saying that it'd be good experience. that was long ago, but everything his father shoved into his hands always sticks around far longer than yuri preferred. he wouldn't call himself an expert, definitely not enough to properly educate a complete beginner. still, yuri's somewhat knowledgeable. more than haru is.
"i dabbled," yuri decides to say so haru's expectations won't end up too high. "father used to make me try out every stringed instrument. i know enough to play most notes on a classical guitar. maybe play a kid's song with confidence. i also know enough to tell that you're not pressing hard enough against your strings, which is why it sounds weird whenever you strum."
most likely, yuri still has his old notes from years ago. maybe he'll bring it back to legacy the next time he returns home. "why did you ask, hm? want me to teach you?" that's probably where this is going. "what's in it for me? you're gonna have to offer me something in exchange. and beg, too. because that'd be hilarious. but let me record you doing it or it's pointless."
he doesn't really mean it—haru should be able to tell. if haru decides he doesn't want to play along with the begging, yuri can do without. he still wants haru to give him something in return... but, knowing yuri, he can also do without that. one of his soft spots is haru himself after all, no matter how much yuri claims on denying that fact. "so, what will it be?" yuri questions, readying his phone in exaggeration. "are you in, or are you out?"
now that he's saying it like that, it sounds like he's pulling haru into a shady underground deal. that won't fare well with any of haru's fans.