Finally tried Black Beacon on my bro's old phone. If I had to crudely summarize the story, it's "Reverse:1999 but with Hack-n-Slash gameplay". Instead of "The Storm", it's "Anomalies from the Black Beacon (aka the Tower of Babel)". The first chapter is pretty confusing, but it does a good job on showing the significance of the MC (called the Seer).
As for the gacha, from what I've read so far, the first copies of 5-star are always guaranteed. After getting the event 5-star, it'll be (I think) 70/30 and not 50/50. Each character has different weapons, so it's a different system compared to ZZZ or Aether Gazer.
It's a good game so far. It's just, that in terms of gameplay, PGR and ZZZ is miles better than Black Beacon. But then again, different strokes for different folks. I think Black Beacon's strong points lies in the setting and character designs.