I didn't know what to expect when I decided to watch this, but I'm so glad I did. The plot was great. It gave me "Your Name" vibes and I happened to watch this right after I just finished Re:Zero so I was able to compare the two. I felt like Re:Zero was very confusing, and a lot of things weren't explained, whereas Summertime Render was straight to the point and still provided thrill and mystery.
Question for the ending: If the people who were supposed to die due to the shadows are alive during the last loop, what about Shinpei's parents?