At least according to his current "roadmap" on patreon, it doesn't seem like there are any other "main characters" to be added, so the current cast is what the options are limited to:
ROAD MAP
[ Completed ] [ In-progress ]
-(11/19) 19 CG illustrations with variations, making a total of roughly 100+ images.
-(0/4) HANA POV: 4 CG illustrations with variations
-(3/3) 3 character sprites with up to 12 expressions and clothing variations: Hana (wife), Yuma and Yuma's neighbor.
-(1/1) 1 main character (husband) side image with expression variation.
-(0/2) 2 Endings. (I'm not gonna bother you with meaningless choices)
-Android version.
-Improved GUI design to fit 1920 x 1080 resolution.
-Classic Japanese-style customizable controls.
-CG, scene, character, and music galleries.
-Flow chart where any scene and branch can be easily accessed anytime.
-Extended configuration settings with a textbox preview.
-Skip read scenes. (just like Fate/Stay Night)
-Name your saves.