Very Nuts For Genshin, Magi Too

Breaking this scene down, it's literally Phainon just trying really hard to strike up conversation, doing his best to try to crack the tough exterior and get Mydei to actually interact with him. He jumps around through topics rapidly--the baths, the black tide, their personal sparring--looking for anything that will catch Mydei's attention.

Meanwhile, we can tell that Mydei is not particularly familiar or comfortable with Phainon yet because his dialogue is so different from any of his other scenes in the game. Although Mydei is obviously not the game's biggest yapper, he does always have full sentences to contribute to other conversations and banters readily with Phainon whenever he's baited into it.

In this memory, he instead starts off polite but also completely aloof:

This is the exact sort of response you'd have to a vague acquaintance coming up and trying to talk to you like you're best friends. Phainon skipped at least four steps of familiarity here, and Mydei is obviously at a loss for why the conversation is even happening.

He responds by blatantly stonewalling, answering Phainon's (slightly pathetic) attempts to start an actual conversation in nothing but single word answers:

You can even see Phainon recognize how bad he's failing half way through the conversation, which prompts him to vocally declare that he's going to make a complete topic switch:

And this time, it works!

When Phainon brings up their personal duel or spar, whichever it was, finally, finally Mydei caves and engages in the conversation with him:

Which prompts Phainon to laugh (in relief? lol) and flat out crow about how he's finally cracked the code and figured out how to get Mydei to notice him:

Poor Mydei, however, did not seem to realize his slight display of interest was going to lead him into a full conversation, and he responds to Phainon's blatant invitation to keep talking with a confused:

Witness Mydei accidentally turning down Phainon's request for a date in real time.

The only thing that complicates the situation is what Phainon says late in the memory: that they've battled "all this time." However, looking at his earlier comments, this last statement may just be in a general sense, as in "two Chrysos Heirs who have been fighting the titans for years," especially as the rest of the line "How do you train? Would you consider teaching me?" once again indicates a lack of close familiarity.

(It's also possible this line is just poorly translated in English, and was actually meant to refer to their legendary ten-day-long duel: "We battled all that time, yet I never saw you fatigued." Given the rest of the lines in the memory, I think "dodgy translation" honestly makes the most sense here, and would also just have really funny implications: Phainon and Mydei didn't fall in love at first sight; they fell in comically-long-duel at first sight. Okay, maybe for Phainon it was both.)

Phainon's earlier statements in the memory make it clear that he isn't very experienced with fighting Mydei specifically, with the overall implication of the dialogue being that they've just had their first duel against each other recently:

So anyway, where I am going with all this?

I know a lot of people got distracted by Phainon's (accidental?) pass at Mydei in the first line, but I think taking a step back and looking at the scene as a whole, in context, makes it even more hilarious and off-the-cuff:

Phainon and Mydei aren't well-acquainted in this scene.

Phainon literally walked up on a guy he barely knows and the first words that fell out of his mouth were "Dan Nicky your bobbies." "I would know that body anywhere."

Even Mydei was weirded out at first!

Like, Phainon has absolute foot-in-mouth syndrome around his new "friend." He spends the whole conversation narrating his own attempts to communicate ("Ah, I see I am unwanted. Instead of leaving, I shall try another tactic. Is it working yet?" and "Yes, yes, yes, it worked!") like this is a remotely normal thing to do around a person you're not even close with yet.

You can see his puppy tail wagging. He wants to be friends with Mydei so bad.

He is actively making up excuses to try to get Mydei to spend time with him here--first the comment about "Yay, you're here!" at the baths like he expects them to bathe together, then the whole "Why don't we go somewhere and have a long conversation about the insights we gained from rolling around in the dirt together?" to finally just flat out asking Mydei to train with him.

It's so charmingly earnest, straightforward, and even a bit awkward that I think this scene is really under-rated by the fans. It's not just another example of Phainon commenting on Mydei's muscles--it's a glimpse into what they were like before they were close and just how much Phainon wanted to connect to Mydei, how willing he was to explore to discover exactly what Mydei would be interested in so that he could seize that common ground between them.

Really a masterclass in showing us fans characterization right on the cusp of changing, and for showcasing both Phainon's charming audacity and Mydei's surprisingly-reserved-around-strangers behavior.

And, since we know the future that memory-Phainon-and-Mydei are headed toward... we also know it worked! Mydei is smiling by the end of the conversation! He and Phainon are going to become vitriolic best buds--er, rivals--and Phainon is going to get all the spars he wants.

Persistence pays off!