As Ryouko’s classmates mistake her frustrated sigh for a lovesick one (though her blushing suggests they’re on to something), Yuliy’s unexpected encounter with his now-vampirized brother Mikhail brings all of his memories of him roaring back, starting with the good times when the two would hunt in the wintry forests of their home—which I imagine to be somewhere in eastern Russia; possibly Sakhalin.
After a good meal with the villagers, the elder laments that the Sirius Arc is no more, but a confident young Yuliy vows to protect it, only for his big speech, like his first kill, to be foiled by a sneeze (he’s sensitive to cold). That’s where the good times end; Yuliy wakes up in the night to find vampires raiding the village. Their mother is killed, but not before making both her sons promise to run away and live. Only one brother can obey; Mikhail sacrifices himself to Yuliy can slip away.
In the present, while reminiscing on all this, Yuliy’s fellow Jaegers try in vain to cheer him up, but the fact is, now that he knows his brother is alive, he can feel his resolve to kill all vampires wavering, as he still loves Mikhail and doesn’t want to kill him, even if he’s a vampire now. His frustration bubbles over when he remembers summoning the power of Sirius to save himself from a pursuing vampire, just when a determined Ryouko tries to confront him.
She isn’t scared of him—or at least talks a good game; we see her trembling slightly—but Yuliy doesn’t want any new friends, because it will mean more people he can lose or who might suffer because of their association with him or their proximity to his powers (Ryouko likely is willing to befriending him, and in any case it’s her choice to make).
Dr. Willard was the one who found him half-dead in the cold, and offered water so he won’t die, Yuliy says if it means he can see his mother and brother again, he wants to die. Willard’s words that follow—fine, die, if that’s what you think your loved ones want—have guided Yuliy ever since.
He may still not know how he should keep living; only that he knows it’s what his family would want, so he can’t give up. But with Kershner, Mikhail by his side, preparing to field some kind of Frankenstein’s Monster, just living—and keeping those around him alive—is only going to get tougher.