If you live near a major city library that stocks anime Blu-rays, you can borrow the physical copy for $0. This is retro but 100% legal.
Since you want the best experience (even if free via trial), which audio track should you choose? natsu e no tunnel sayonara no deguchi free
Recommendation: Watch the Sub first. The phrase "Natsu e no Tunnel" (The Tunnel to Summer) is a poetic pun that sounds better in Japanese. If you live near a major city library
If you are on a budget of exactly $0, follow this moral and legal guide: Recommendation: Watch the Sub first
Result: You watched it legally, for free, without malware.