It hasn't been officially translated (yet, I seem to recall Spike making a Switch port announcement?).
You're not missing much, though. The best of the side stories there is, like, on par with the weakest one in LBP.
A few weeks ago I finished Muv-Luv Alternative. My time reading it was an enjoyable one, while the time investment made across three games can't be called small, I feel the payoff was proportional and well earned. If I think about how Muv-Luv Extra started and how I was relatively lukewarm towards Takeru's character initially, I'm a little surprised that he gradually becomes aware of his shortcomings and how his relationship with his peers helped shape him into the person he ultimately becomes in Alternative. He managed to achieve most of the things he set out to do at the beginning of the game, but at the same time, if we're already familiar with these kinds of stories, chances are he'll be doomed to fail, or the result would be a pyrrhic victory.
The world of Muv-Luv Alternative is a harsh one, therefore even if everything is going Takeru's way, the loss of lives is not something that can be avoided. And when a mistake was made, we were reminded that the sheer absurdity of its ensuing effect will transform our protagonist's resolve into hopelessness. Up to a certain point in the game, Takeru is full of confidence, ready for any challenges to be thrown at him. But when the going gets tough and shattered his confidence, he wallows in self-pity and refuses to listen to his peers who tried to reach out to him. Ultimately, he did something unthinkable for a protagonist by running away to his supposedly 'safe space'. Kasumi, in particular, speaks for the audience when she told Takeru what she thinks about his action. This one particular arc stood out to me because running away from responsibility is a completely human reaction. Takeru's character in Extra is one of an under-achiever. However, his peers in Alternative expects him to be something much more, as Meiya exclaimed, he is destined for great things, and he must be able to answer their expectation, for better or worse. The development of Takeru's temperament related to these expectations and how it influenced his peers' in return across three games is something Muv-Luv as a series truly excels at.
Since Alternative is mostly plot-driven for the second half of the game, Takeru didn't spend as much time with his original squad members, however, his interactions with the rest of Isumi's Valkyries played a big role in affirming his resolve. His conversations with Captain Isumi and how she copes with the loss of her squadmates put a lot of perspective into Takeru's point of view. One particular conversation which stood out to me was the conversation they had before the attack on Sadogashima Hive about their personal goals, and the importance of sacrifice. If we recall Takeru's struggle to rationalise human sacrifice during the early game of Unlimited, to have him finally be able to grasp the point of views of his peers' is something of an inspiration.
The ensuing attack on Sadogashima Hive is also a major highlight of the game. It's good to finally see Takeru with a newfound conviction and confidence once again. Of course, not everything goes to plan, since they had to defend their base from another BETA attack almost immediately with reduced fighting strength. Again we were reminded about the nature of sacrifice and the cost of victory. The tension from this point onwards didn't let up until right to the end of the game, with the only respite is the pre-mission memorial visit, which of course triggered a bunch of death flags.
If we're not already aware of how costly sacrifices can be in this game, we can be sure that it won't pull any punches in the final confrontation between our heroes and BETA forces in the deepest recesses of Original Hive. And then, comes the epilogue. Learning the truth about the nature of Takeru's Causality Conductor status is almost to be expected, although I won't say that I saw it coming from a distance. There's plenty of touching moments right up until the end of the game, and there's also plenty of catharses which left me feeling pensive and fulfilled at the same time.
While I enjoyed my time with the game immensely, I'm still not sure if it actually deserves the top spot in Vndb. It deserves its fair share of accolades, for sure, but 7th Expansion's titles would probably be more deserving for the top spot, in my opinion. Although perhaps, it all comes down to my personal taste. Regardless, Muv-Luv Alternative is a great read, I can heartily recommend it, and I'm looking forward to reading both photonflowers* and photonmelodies♮ , and hopefully, someday soon, Integrate.