Keiko Everlasting

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. It mostly fits into the Iyashikei genre, although there is also a tragic element to the story. There are a lot of characters and all the main ones, of which there are 16 (20 if you include two sets of parents), have voice acting and multiple expressions. It's not too many characters, however, because half of them are present in the first half of the novel and the other half are present in the second half of the novel.

Character list:
Keitaro - Main character. Smart, innocent, and 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 school eSports team.
Shino - A study-bug who is equal in intellect to Keitaro, but more academically inclined.
Ayuna - Yuri's best friend. She has a lot in common with her personality-wise, but also takes an interest in Noriyuki.
Kadan, Joji, and Orino - Haruko's friends who all play for the school football team. Kadan is a giant goofball, literally and figuratively. Joji is his loyal sidekick who fails to prevent him from making a constant 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 as much as he tries to prevent Kadan from making himself look like one.
Mai and Tomomi - Keitaro's parents. They're a warm, simple couple.

The characters all swap out for a new set in the second half of the story, except for Keitaro who stays present throughout. Many of these other characters have similarities to the first set. The remaining characters consists of:

Rinji - Another goofball who is extremely animated (without any literal animation, of course). He is constantly trying 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. Her braided hair gives this affinity away right off the bat.
Aiko - Keitaro's cousin. He is a video game developer, embodying the other side of Noriyuki in conjunction with Takeo. He is also a passionate futurist who has complete opposite beliefs from his sister. They bicker often.
Kasumi - Super bubbly and kind. She always finds a reason to stay smiling or laughing. She's 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 fun progression from friend to lover. One such difference, for example, is that she is highly confident and he is not.
Tamiko and Michio - Keitaro's aunt and uncle. Tamiko is responsible and protective, and Michio is another fun, hearty goof.

There are a series of adventures in the first half of the novel with Keitaro and his friends/siblings. The second half of the novel, with the second batch of characters, progresses into a more developed and committed storyline. This "half" is actually more like two-thirds, because it is longer. This part of the story has more depth, however.