The creator has been on the warpath with blog posts. Most of it is a mix of apologizing, explaining he's still working on the new game (and how), and plans for updating his very first game. He intends to do this through a service called Ci-en, which can be likened to Japanese Patreon. The fifth game will apparently be released on DLSite either way. In the meantime he is directly answering individual replies to his blog posts.
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(RJ215801) received new scenes as of 08/30/19. The game also includes a folder of "experiments" consisting of whatever game engine interested him at the time, but sadly they aren't as ambitious as the one he threw into RJ181767.
09/03/19: Something about adding more to a current RJ that includes this character.
He mentions the update date will change when it's available, but it hasn't yet. Appears as playable in another side-scroller experiment (no H) and in her own RPG battle, as an enemy (which has H.)