It's a sequel, so that it's a bit lower than the first game is a possibility that the developers should have taken into consideration when they greenlit the project. I think that they wanted to avoid a lower opening by bringing the game to PS4 as well. Looks like that didn't help and the two platforms didn't expand the fanbase beyond those interested in the first game. It's a shame, because the first game was very lovely. Yomawari: Night Alone did a good job on Steam (24,300 owners according to SteamSpy) and hopefully had decent success in the west, which could justify development of this game for all platforms that it's coming out for.
Such a shame that NIS's recent efforts didn't pay off. Yomawari looked like a game that could turn into a small but nice series. Hopefully that's still the case... But after the flop Witch and the Hundred Knight 2 was and how games like Exile Election and Hakoniwa Company Works didn't work out, it doesn't look too good for the company. Coven and Labyrinth of Refrain did very well on Vita, but I doubt the PS4 version will add many sales to it in Japan. The dungeon RPG genre is very niche in the west and I'm not sure a PS4 version will save the day for this game if/when it gets localised.
Maybe the Switch can help out. NISA is bringing Penny-Punching Princess to the Switch in addition to Vita. I haven't seen any confirmation of the Switch version getting a Japanese release tbh. After the success of Disgaea 5 (mostly in the west), maybe a Switch port could help a couple of games expand their market. Hakoniwa Company Works is built in Unreal Engine 4, so that shouldn't be too much work to port to the Switch OS (hopefully the game can run decent on Switch hardware). I'd say Yomawari 1+2 would be worth the try too.
