Reideen summary:

From Cireus-Anime website: Saiga Junki is a normal high school boy who tends to be a little apathetic in general but who does manage to get better than average grades. When his archaeologist father, who went to investigate some ruins, is found dead, the family travels to the excavation site where Junki meets a mysterious stranger who gives him a ‘gift’: an ancient artifact that his father left for him …