Keiko Everlasting

Disclaimer: Some might not consider this a video "game" since there are almost no player choices and there is only one ending, but it is a far cry from a manga and can only be experienced on a computer. The name for this is a "Kinetic Novel" -- a subgenre of Visual Novels. You still click through at your own pace, of course, like any other VN, as well as save, load, and view a backlog of what you've recently read.

This is a linear story about a teenage boy named Keitaro Soseki from Kagoshima, Japan. It is a Slice-of-Life romance novel with lots of comedy as well. For those familiar with VN genres, most of the story is considered "Iyashikei", but there is a tragic element as well. There are 20 characters with voice acting and expressions.

Character list:
Keitaro - Main character. Smart, innocent, a little shy.
Yuri - Keitaro's younger sister. Bubbly and bright.
Haruko - Keitaro's older brother. Sporty and mature...for the most part.
Noriyuki - One of Keitaro's best friends. He is obsessed with girls and plays competitive video games for the high school eSports team.
Shino - A mature and reserved study-bug with a thing for Yuri.
Ayuna - Yuri's best friend. Has an interest in Noriyuki.
Kadan, Joji, and Orino - Haruko's friends who play for the school's American football team. Kadan is a giant goofball, literally and figuratively. Joji is his loyal sidekick who constantly fails to prevent him from making a fool of himself. Orino is the wisest of the bunch, often scolding Kadan for his clunky behavior and trying to prevent himself from looking like an idiot in their presence.
Mai and Tomomi - Keitaro's parents. They're a warm, simple couple.

The characters all swap out for a new set in the second part of the story, except for Keitaro who stays present throughout.

Rinji - Another goofball, extremely animated (without any literal animation, of course). He frequently tries to impress Kasumi.
Takeo - Just as obsessed with girls as Noriyuki, but is a little smoother about it.
Hana - Keitaro's cousin. She has a passion for spirituality and her head can be in the clouds at times.
Aiko - Keitaro's cousin. He is a video game developer and sometimes reminds Keitaro of Noriyuki. He is also a passionate futurist who has complete opposite beliefs from his sister. They bicker easily.
Kasumi - Bubbly and kind. She is always smiling or laughing. Despite her excessive cuteness, she is smarter than she looks.
Keiko - Keitaro's love interest. Wholesome and sweet. She has significant similarities to Keitaro but also complementary differences that make for a natural progression from friend to lover. She is as confident as he is shy.
Tamiko and Michio - Keitaro's aunt and uncle. Tamiko is responsible and protective and Michio is a fun and hearty goof.

There are a series of adventures in the first part of the novel with Keitaro and his friends/siblings. The second part of the novel progresses into a more developed and committed storyline with much more depth to it.