Soooo this is based around the song 'Last Christmas' by Wham, (you can listen/watch on YouTube The giving a heart isn't supposed to be literal but well, this *is* Dazai...

The death is not detailed it just sorta happens

Last Christmas I gave you my heart.

It had been a gift a year in the planning.

Dazai had never known what to get the man who had everything.

He had managed to hold onto life long enough to present Chuuya with the gift-wrapped box, his boyfriends look of surprise the last thing he saw as a human. He had assumed that the afterlife was a black nothingness but instead he lingered, a ghost able to see what happened next.

But the very next day you gave it away.

If he still had a heart it would've broken, when the next day Fyodor turned up and Chuuya gave him Dazai's heart. They laughed and laughed before throwing the body part on the fire, the flames quickly engulfing it and Dazai's love for Chuuya.

Once bitten and twice shy

I keep my distance, but you still catch my eye

Kunikida – another ghost who'd died in a similar manner, told him he should stop following them. That from his own experiences he knew following a human love wasn't worth it.

But Dazai couldn't help it. He was fascinated by the changes in his Chuuya and how Fyodor was just a Russian version of himself. If only, if only his gift had been what Chuuya wanted.

Tell me baby, do you recognize me?

Well, it's been a year, it doesn't surprise me

It was Christmas Eve again, Kunikida had joined Dazai to watch Chuuya and Fyodor, the two ghosts had grown close over the year. As they watched, both with longing in their eyes, Dazai realised, Fyodor was Kunikida's ex. They both cried as Chuuya proposed and Fyodor nodded 'Yes.' They floated away, unable to take watching their ex-lovers any longer.

This year, to save me from tears

I'll give it to someone special

As they comforted each other, drying the tears. Dazai wished he had another heart to gift, as in that moment, he knew.

Kunikida was his someone special.

A/N You can also find me on Twitter and AO3 as Darke_Faerie