[Version 0.2.7]
Tennis Ace isn't your standard, run-of-the-mill eroge game featuring gay furries. Although sex and romance are present, the game focuses on delivering a story with interesting characters in the mix, all with their own personalities, secrets, flaws and goals in life. In a sense, Tennis Ace is more of a proper VN than an actual eroge.
Let me warn you right now - romance is a slow-burner on this one. You will have to chug through a lot of content and story to get to the "meatier" parts. Despite being in development still, the version I've played has quite a few hours worth of content and I still haven't managed to romance (much less have sex) with a single character; I'm unsure if by poor choices or because the story is still building up. For a game that I assume is still early in development, it is both impressive and a tad frustrating.
Nevertheless, I find the quality to be far superior to what you'd normally find around here, both in terms of writing and graphical design, which makes the waiting more manageable.
Now, you may think of it as obvious but this game focuses a lot on tennis; if you're familiar with the sport then you will be right at home with this one for it deploys a lot of technical terms during the matches that will leave those less informed (such as myself) scratching their heads. It can be a tad overwhelming at times... maybe even a little boring. There's a visual representation of the ball's position and angle in the court before and after contact, which helps the reader visualize what is going on and adds up the immersion. (To clarify, the matches are mostly automatic though there are some rare occasions where you're given a (timed) choice.)
Overall, Tennis Ace is a breath of fresh air compared to the shallow and 2-dimensional eroge games you find about. The quality is superb and the characters are interesting and believable.
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TL;DR - Tennis Ace is less of an eroge and more of a proper VN with several hours worth of high-quality content... though it may not be for everyone. The pace is slow and deliberate and it takes time for characters to open up and reveal themselves to you. If you're only here for instant gratification and faps, then I wouldn't recommend it. If you're into tennis and like a good story though, then I believe you will enjoy this one.