Sweetest Monster is a Kinetic Novel (= no choices involved) presenting a ~3 hour long read accompanied by eerie music and sound effects which will lead you to a mysterious yet nostalgic universe.
The art is really well done, both character sprites and scenery are awesome. The story presents some plot twists, yet, from another perspective it's quite realistic and relatable.
I'd say the main topic of this game is life. How some choices might alterate the situation you are living (and sharing with your surroundings) significantly, and, eventually bring you a dreadful sense of guilt.
Characters are well presented, relatable personalities, interesting traits, nice coloring.
+Also, some fanservice is presented but it's not the main point of the story.