The brightly shining firefly
Disappears into the dark
So fleeting and so meaningless,
Just like my yearning heart
—Firefly's Light
Profile picture is Igarashi from Kobayashi Kina's A Lazy Guy Woke Up as a Girl One Morning, chapter 20. You should read it. (Chapters 17 and on aren't on MangaDex anymore, though, so you'll have to find them elsewhere...)