So that's it... Show's over...
In regards to the last episode itself:
The kids have taken a major leap and shown that they're now capable of conducting Raids. Particularly Minori. As the Raid Team's leader, she may have been a bit shaky in some moments, but her Raid team had her back. And in which she was able to use "Full Control Encounter", although it was on a smaller scale. But it shows that she's improved as an adventurer.
Then, of course there's her love confession towards Shiroe. Even though it wasn't all that surprising how it went, it's rather needed for Minori to move on & grow as a person. Also, it's good that this part of the story had proper closure.
But one thing I did not expect is that Shiroe is interested in Romance. You'd think a person like him being occupied with his works as Guild Master & being a key person in the New Round Table wouldn't have the time for things like Romance. Color me surprised on this.
Let's not forget about Isuzu for a bit here. It's a good thing that she came to the realization that egging Minori on about Shiroe was a terrible thing to do. Rudy for the most part was already aware of this, but I felt that Isuzu herself realizing her mistake & admitting to it instead of Rudy pointing out to her is the better way for Isuzu to improve as a person. After doing such a thing, the best thing for Isuzu to do is being there for Minori after she got turned down. And seeing Minori like that, was a little tough to watch.
Now, with the matter with Eirenus done, comes the next major thing; Visiting Minami. The last time we've seen Minami, it was on the path towards Civil War. I'm presuming that Shiroe wants to establish diplomatic relationships & a possible alliance with Minami because of the threats of the Geniuses.
The Geniuses are not just a threat to the Adventurers in Akiba, but to everyone. We've seen them in the act before, it's not just this season with Papus & Eirenus. There were also other Geniuses we saw in the later parts of season 2. And now after the attack by Eirenus, Shiroe must know that the Adventurers can't handle this threat by acting on their own. So he must be planning this visit to Minami to form a diplomatic relationship & a possible alliance to fight the Genius Threat.
Think back during the Election episodes this season, it was mentioned that some key figures in Minami wanted to have peace talks with Akiba instead of going to war with Akiba.
So that's basically it in regards to season 3.