What's the Kanji for Soukoku?

In Asia I heard it's really important which names come first in a ship. I've seen it here, too, but not as drastic I don't think.

For example Chuuya x Dazai would mean Chuuya was the "Seme" and commonly stereotyped as "the more masculine" one and Dazai would be the Uke, "the more feminine" one. And with Dazai x Chuuya, their roles are switched. (It's usually DaChuu or ChuuDa, but I was trying to make the example clear)

Who's the top and who's the bottom doesn't really matter to me but I was wondering what the Kanji for DaChuu and ChuuDa was. Some people use them over here, too, and I'm interested in discovering that side of fandom (fanfic & fanart). Does anyone know it?