It starts with his failing yet another marriage interview, and despite him fervently studying books to be popular/understanding women's heart/and other ? books, he always gets turned down. He resolves against having a r/s with women(?) from then on OR SO HE THOUGHT IN HIS HEART but then!! the girl appears at his doorstep with his boss behind her.
Under his boss's request they stay together (dont ask me why I'm not high level enough for their convo). I think the girl is the boss's daughter. Anyway it's something she wants as well + the boss trusts him in this matter so he gets persuaded. He recalls finding her familiar, because when she was a little girl, she served tea to them during their meetings. Suddenly he runs to the park to spray himself with fountain water because apparently it's his first time having a roommate and because it's his boss requests he will protect her and not do any pervy (?) things to her?
Imma skip the living together goodness and save it for when it gets translated.
Good/bad things happen, which prompts her to propose to him at page 41.
Flashback to when she was a kid, she asks her dad "what is marriage for?" and dad answers "it's for you and the person you love to be together forever." and she has that "omg i want that too" innocent expression.
Jump to the classroom, she's elementary year 4 (that's 9-10 years old), she writes that she wanna be a bride in her "shourai no yume ( things she be/do in the future you know what I mean) form. on the way home her classmates teases her and she says she doesn't know what kind of person she wants to marry yet.
She's home, and MC is there !! Not sure what they're doing sitting side by side (they both seem to be doing their own work?) but he's commenting on her calligraphy or stroke or penmanship(?). Skip their session together, we see her walking home again and she's like "i'm not good with MC... I definitely don't want to marry that kind of person." OR SO SHE DECIDED IN HER HEART (yes that's the last panel of pagr 47) .
So we skip back to where her proposal at page 41, now we're at page 48. He asks her to repeat, small text "did I hear something about marriage...?" and she blushes, stutters, then the next page skips to her parents. I don't get it but it basically reveals the reason why the boss had them stay together (sorry, i know this is the crucial backstory y'all wanted but im not confident in translating it. The middle/largest speech bubble just says something like "these roommates are good medicine for each other" in direct translation).
Skip to them living together, not sure what happen but he was on a phone call and after the phone call she asks him "is it true that you plan on never getting married?" He says "it has nothing to do with you(the kanji for you here being Child/Kid). Hurry go sleep." She cries herself to sleep.
The next morning was a lil awkward but as they walk out of the door he apologies for letting her hear the phone conversation he had and asks her to forget it. She starts telling him "you may have forgotten this but..." (flashback to when she was in grade school and both her mom and MC are at the same table) The mom is telling him about her "future dream" form like "when you talk about the future, don't you usually write down an occupation? she wrote that she wanted to be a bride" but MC said "marriage is serious business so wanting to be a bride is a splendid dream". Our 4th grade MC tears up (end flashback) continuing her speech she says "he's the only one so far to take her dream seriously and she says it made her really happy". He looks confused and says "dream? sorry what are you talking about?"
She grabs her hand and declares "I want to be MC's bride!" on page 70. Page 71-72 go see it for yourself.