Ushio and Tora

It centers around the travails and battles of Ushio Aotsuki (??? Aotsuki Ushio), who is constantly being stalked and aided by a gigantic, supernatural and sometimes invisible tiger-like monster (somewhat like Calvin and Hobbes). Ushio s family maintains a Shinto temple in Japan, where ~500 years ago, his samurai ancestor battled that same tiger to a standstill, and eventually trapped him against a rock using a blessed spear called the Beast Spear, which in addition to its intrinsic formidability as a weapon, can also endow its wielder with the martial ability of the ancestor who originally wielded it. Ushio accidentally unsealed the cave Tora was trapped in. Initially, Ushio refuses to remove the spear pinning Tora (??, Japanese for tiger) down (as Tora made the strategic blunder of mentioning that the first thing he would do upon being freed would be to devour Ushio), but Tora s unsealed presence summons various monsters who wish to fight him, and by extension Ushio.