I Married My Female Friend vol 1
Another first volume, although no sign of volume 2 yet. The series has ended in Japan already on 4.
2 friends make a deal to get married if neither are in a relationship in 5 years. So, of course, this is what happens, otherwise the title would be a lie! One, Ruriko, is pretty straight laced, has a proper job and goes to bed at sensible time, etc, whilst Kurumi is freelance journalist, goes out most evenings and then pulls all nighters to get her articles in on time. Ruriko definitely has a thing for Kurumi and seems totally fine with the arrangement of Kurumi going off and doing her own thing, for now... Kurumi in the meantime is totally oblivious about Ruriko feelings and doesn't take the partnership side of marriage seriously, they're just best buds living together in slightly odd circumstances after all, for now...