Isn't the game finished? You defeat the demon king at the end.
I guess the story is finished but according to his twitter posts during these past months it seems like he does plan for additional stories different from the main one, with new characters and stuff
There's a GBH CP3 (Chapter 3) in development. If you search this thread you'll find a link to a fight he's made with a new opponent.
Unfortunately (IMHO) what he's done with GBH is more akin to UFG Type A, B and UFG 2... which I'm not a huge fan of. When I'm playing a game, I don't mind the RPGM grind or puzzle solving aspects, but Boko877 isn't great at presenting a balance between guiding players to the path of victory and straight-up telling players how to beat his games. He's great at balancing fights based on what tactics you need to take to win, but bad at giving you decent hints at what those tactics are. The UFG series that I've played focuses on learning a strategy through getting your ass kicked mercilessly and repeatedly... sometimes hopelessly, until you figure out "the secret" to win. GBH is a little more forgiving.
But then he gives you a hint file that basically tells you "I made this way too exhaustingly difficult for an average player to figure out, so here's what you need to do!" Or, in GBH, he gives you a tool that lets you max out on your stats as part of the game.
I mean, I wouldn't mind at all failing in a quantity not exceeding single digits (I am a fan of getting my ass kicked by powerful sexy ladies) as long as I'm getting a tiny little bit of "the secret" each time I get punked, because I don't like games the are way too hard to win. With Boko, it's either a task too frustrating for your average gamer or too easy to be considered an actual game. I love big powerful boobs enough to be a fan despite this, but I wish he'd take the simple steps towards making his games a little more gamer-friendly.
But no, the story's not finished... just the chapter.
I'm hoping for a chapter involving routine "Magicquakes" which buff the opponents in balance with the player's projected stats so that you can may or may not get your ass kicked in any fight regardless of how much grinding you do to level up. It bummed me out that I could exploit repeatedly beating Eriferu for tons of EXP and nullify the challenge of defeating the rest of the enemies.