After trying out a few of these games, I seem to have finally stuck with Chain Chronicles and Marvel Puzzle Quest (I'm surprised I haven't seen this one mentioned at all in this topic. It isn't Japanese, but it is definitely a gacha game, and it's actually the one I've been playing the longest.) It can be pretty frustrating as a f2p player, though. It's fine at first, but once you make it past 2* characters and start getting a good team of 3* characters it gets really frustrating without actually paying money for drops. It's still good to log in and play for a bit at work during downtime, though. Same with Chain Chronicles (which I've been treating very casually. Haven't really even gone very hard on the gacha in that game, just been using my starter characters and Nimpha.)
I've also been playing Galaxy of Heroes for the past week, and it's held my attention for this week pretty hard, but I'm not quite sure how sustainable it is without actually dropping money into it. Hell, I dropped $5.00 on it almost right away with a Sith bundle it offered me, and I honestly don't think I'd be doing as well/getting as far as I have been without having bought that. $5.00 isn't bad, though it then offered me a $25.00 Droid bundle, $40.00 Jedi bundle and finally a $50.00 Heroine bundle. KOTOR nostalgia eventually got to me and I got the droid bundle for HK-47, but I have to admit I kind of regretted it afterwards. I only did it because I had some google play credit from buying a new phone, so it didn't actually cost me anything, but I really don't see how you could compete in this game without purchasing something. It would be a really bad grind of just playing the same starting levels for a really long time.
I tried Brave Frontier, Dragon Blaze, Puzzle & Dragons, Blood Brothers 2, and Terria Battle. Terria Battle didn't really turn me off, per se, as much as I just got caught up in other games. I was logging in daily until it gave me a server error one day, and then when I tried to log in later that night it said I had missed a log in and killed my 30 something day streak. Since then I kinda just gave up on the game.
Dragon Blaze was just boring, and Brave Frontier was like a slightly better gameplay wise Dragon Blaze but it looks way worse. I can't get into the art for Brave Frontier AT ALL. Seemed like an OK game to play while watching TV or something, but ultimately it didn't hold my attention.
Blood Brothers 2 had a really cool art style, sort of like Darkest Dungeon, but god the game play was really boring. It was a bit better in the PVP mode, but I also needed way better characters to compete in the PVP mode which I just wasn't getting. It was essentially an endless game of rock paper scissors.
Puzzles & Dragons I played for a good month or two before getting frustrated with unlocking cool monsters/evolving cool monsters and not being able to use them in my team due to not having enough points. I have all these cool gods and I can only use one or two on a team at once?? It just turned me off from it. I still log in daily though, haven't deleted it like I did with Brave Frontier and Dragon Blaze.
If Phantom of the Kill actually plays like Fire Emblem I'll be pretty interested in checking that out. Don't know why but I love trying these games out. Most of em last me a couple weeks to a month at best before I tire of em though. Trying to find the next Marvel Puzzle Quest that will keep me playing for months (I started playing Marvel Puzzle Quest back in May or June, still log into it and play daily. Not as hardcore into it as I was though, due to the grind mentioned before).