Golden Time Anime: How did Banri lose his memories?

Golden Time Anime has spent quite some time into the passage of time. Yet today we dare not from asking, how did Tada Banri lose his memories? Is his amnesia realistic?

Rewatch] Golden Time Episode 24 Finale Discussion Thread : r/anime

RevYou - Golden Time Review

Golden Time – 08 – Random Curiosity

Anime Review: Golden Time : r/anime

Rewatch] Golden Time Episode 24 Finale Discussion Thread : r/anime

Adjusting to college life is hard enough for most students, but ever since Banri Tada lost all his memories he's literally being haunted by the spirit

Golden Time: Collection 2 [Blu-ray]

Golden Time Response – Mage in a Barrel

Golden Time - 08 - Lost in Anime

Review for Golden Time Collection 2

Golden Time, Banri regains his memories for a second and tells

Golden Time (novel series) - Wikipedia

Golden Time Has Great Romance, Comedy And Drama -- And A Terrible

Golden Time – 07 – Random Curiosity

Golden Time – 10 – Random Curiosity

Banri Tada Is Dying.