I hate these kind of "endings" where the story is clearly over, maybe an epilogue or two needed, but then the author decides to pull some BS and say there's more to come.
This is 16.1? This felt like a complete chapter and it was so good you could even consider this an end to the series. I wonder where things will go from here, probably something to do with the machine that they found from the past. I'm gonna just guess that Leo isn't the only one alive from the 12.