There's a Reason Why I Can't Get Married.
結婚できないにはワケがある。 · けっこん できない にわ わけ が ある
est. Rough estimate based on volume count, reprints and magazine — not an official figure
Overview
I want to be married... And someone like Tomizawa would be perfect! Mariko, 29, wants to seal the deal by 30. However, marriage requires affection and Mariko's affection is reserved to a man she can respect! She's single at age 29, also aware that she can't let go of her pride. One day, a chance to date THE ideal-candidate, Tomizawa, falls right into her lap!! Delusional or not, she can't let anything jeopardize her opportunity to hear those wedding bells ring. A chaotic private life and dramatic sequence of events keeps her on her toes. Is marriage even on the table?! (Source: MangaPlaza) Note: The digital version has six volumes.
Source: AniList
External databases: MADB · AniList
How to compare editions, collected volumes and ISBNs / Sources, updates and corrections