Lavina is his alter-ego, his civilian indulgence; flameless, soft, pretty, and talented in a way that he can't show off in front of the wider mafia. But she also leaves him vulnerable in other ways. Vulnerable to falling in love, to being seduced, to spread his legs for a man that flatters him - to forget that the illusion is complete.
It ties up most of his Flames and other defences, that illusion, and it's not until Don Falco - and he laughs in bitter hysterics when he realises that the man that had seduced him is a Don, one who'd even tried to contract him as an assassin - has him installed in the 'family' castle with a midwife he recognises that he realises how deep down the rabbit hole he'd allowed himself to fall - and that 'stopping' being Lavina will mean losing the tiny flickering ball of Stormy Flames and attitude incubating in his womb.
He ends up killing his way out - slitting more throats than he means to, leaving the young heiress as Donna presumptive (given that she already has poison cooking, he suspects that she'll be okay, especially since a decent proportion of the Family are long term retainers) and, given that Lavina is a legal entity with a Japanese passport, makes good his escape via that route.
Japan is fucking touristy until he really embraces the role of Lavina, and starts indulging in wearing furisode in the sort of prints that fit her persona. It emphasises their Japanese heritage enough that people stop treating him as a tourist, and the Flame 'wards' on the yakuza's playgrounds stop repelling him, too.
Which is how he notices Tsuyoshi Asari. It's only acute senses that let him spot the odd fluctuation in the man's Flames through the mess that grief has made of them, but it's the way the raging tempest in his womb calms when he's near the man that has him approaching him. Hayato - he's already named his little tempest, a wish for him to fly on his own unclipped wings - flares in delight, and there's an answering flare from the tiny anomaly in Tsuyoshi's Flames.