I don't think the author will break the integrity of the story but might add a fling or small relationship to help mc realize that he really loves being single. Also about this, I don't think mc has any 'relationship" thoughts with her but finds their relation to be something unexpected
yea 57-58 as @Heavenstar said, but i'd say start from 55, so that it will be easy to transition into the story and also keep an eye on side chapters in raws, as further side chapters aren't translated
I've put it on last line of that page, but here it is
https://m.fanfiction.net/s/14204148/1/Ghost-of-Kyiv-an-Azur-Lane-Story
And if you'd like to talk with the author, just hop on the discord server