Of all the characters fleshed out in this book, I came away with a better understanding and even appreciation for Chiba (the idiotic classmate of Haru's who was transported into this world too when they died). Though there were still a few sad parts, I appreciated the overall lighter tone of this book in comparison to the original, which got pretty bleak at times. In that respect, I would say it was a success and I really enjoyed it. However, Summer is different from the original in that it's a series of short stories told mainly from the points of view of side characters, instead of Haru, and fleshes out their backstories. Thankfully, J-Novel Club was able to license it through Hayakawa so we could read it.
JK Haru: Summer is a semi-sequel to the original JK Haru that the author self-published in Japan.