Hahahaha, I head!canon that when Mikoto sings lullabies to Anna, they’re all *not* songs that should be lullabies. Like, he’s signing classic rock shit like, “Centerfold” or like Nirvana or other shit that one should not sing to a child. And you’d think Anna would mind, but she really doesn’t because you’re absolutely right, Mikoto has such a lovely singing voice that she doesn’t care at all what he sings, she just loves hearing him sing.
And yeah, so one night, Reisi decides he’s going to surprise Mikoto with a late-night booty call, but no one told him that Anna’s sick and Izumo’s out of the country and so Suoh is babysitting. She’s got this awful fever, and she’s just enervated beyond belief, and so like, he gives her some ibuprofen to bring her fever down and he’s just settled her in bed and he starts singing NIN’s “The Perfect Drug,” which is *definitely* not a lullaby.
Meanwhile, Reisi’s just come in and he’s tiptoeing towards the bedroom and stops as he hears Mikoto’s voice. And of course he laughs to himself, because, like, that is *not* a kid’s song, but Mikoto’s voice is sooooooo sexy and the fact that he’d sing Anna to sleep is so endearing that Reisi just falls in love all over again.