So, as stated by others, the date itself just started in the newest chapter, 354, but since it is really only the very beginning, you could maybe still say that it hasn't really started. However, what happened: Mami appeared again ,we get more information about her, her current state, her inner thoughts. Probably the only really decent part iswhere Kazuya went on a date with Mini. More precisely, he called it a "practice date" to rehearse the actual date with Chizuru, but, yeah, Mini acted a bit different from usual (in short: there were hints that she might see him in a romantic way) and it seems Kazuya saw her for the first time not only as a friend, but as a woman. Nevertheless, he more or less immediately put it aside.
My overall impression: Mini and Kazuya would be a better fit for each other, they have better chemistry, they act more or less normal with each other, etc. Unlike Chizuru, which behaves still as cold and stupid as ever and Kazuya overthinking and panicking all the time, as usual. So, the best moments of these 30 chapters are when Mini acts all weird and shy around him for some pages, but that's it.
tl;dr: Mini and Kazuya show a lot of chemistry with each other for a brief moment in time, have fun and otherwise, it's rinse and repeat, no real progress.