I started playing the original version of this and the remake dropped before I finished, so I switched over. The Doukyuusei remakes are a lot friendlier since you can jump from flag to flag instead of wandering aimlessly around town, killing time, and trying to follow a guide. The art is also updated in the remakes. They were very faithful, so it's the same situations, poses, etc. with a newer, better art style. I did play the 18+ version, of course.

This is one of the games that really exemplifies what a dating sim is. This isn't some visual novel where you make a dozen or so choices and get locked into a 20-hour route dating one girl. You run around town talking to girls and progressing multiple, much shorter routes at once if you choose. Using the flag jumping you can do an entire route in an hour or so. Doukyuusei 2 has 15 romancable girls covering a good range of tropes.

• Yui - The MC's non-blood related little sister and essentially the main heroine. It's her face on the taskbar icon and she's possibly the most recognizable character from the entire franchise. She's got the hots for onii-chan from the start and is a good girl.
• Tomomi - The childhood friend who lives next door. I didn't really care for her route since she's pretty cold throughout most of it.
• Izumi - A tomboyish girl who does archery. Her and the MC give each other a lot of shit. One of the better girls.
• Karen - An idol who is rarely at school. She's a sweet girl, but the route is nothing special.
• Minori - The cute girl who intentionally dresses plainly. I found her kind of annoying and her sex scene is a bit on the rapey side (there is no actual non-consensual sex in the game.)
• Youko - Rides a motorcycle and acts kind of like a delinquent. One of the better girls and routes.
• Sakurako - The sickly girl. She spends a good chunk of the game in the hospital with you climbing a tree to talk to her. She was apparently considered kind of a hidden route and was about as popular as Yui.
• Kozue - She's the library girl and does tennis. I honestly don't remember this route well. She's the youngest looking of the girls and kind of childish, but she's still a high school girl, not a loli.
• Kumiko - The hick who admires city life. She lives at her family's inn in the mountains and runs away, staying at the MC's place. She's meh.
• Misa - The only girl to make a return appearance from the first game. You remind her of her ex, who is presumably the MC of the first game.
• Aimi - A day care worker. She's adverse to guys at first but falls for you cuz you're such a nice guy to kids.
• Misato - A tour guide. She's the guide when you take the bus to the inn Kumiko works at. This sex scene was also a bit questionable.
• Mirei - One of your teachers. You console her after her boyfriend dumps her for caring more about her job than him. Unlike the teacher route in the first game, you actually seal the deal this time.
• Misako - Yui's mom who took you in when your dad died. She loved your dad and now you love her, as more than just a mom. Definitely a bit of an awkward route, but she's a great lady.
• Sachiko - Kumiko's mom who runs the inn. This woman is thoroughly forgettable.

The remake also included the bonus route for Sakakibara Miyuki from Sotsugyousei. I didn't actually read this route, but she's cute. Ultimately it's not much different from the first game. Which you prefer may simply boil down to which characters you like more. Hopefully they remake the Kakyuusei games as well. I don't know if there's been any official announcement, but there is some background advertising for Kaykyuusei in the game, so it seems likely.