Kekkon Suru nara Ore ni Shiro: Slow Wedding wa Haran no Hajimari

Iroha had a solo wedding on her 30th birthday. But the next day, her ex-boyfriend, whom she broke up with 8 years ago, comes to her and says, "I'm not over. I've been looking for you for a long, long time."
https://www.cmoa.jp/title/275599/