A former professor of archaeology, Hieda Reijiro, was expelled from the Japanese Archaeological Association for claiming that youkai exist. Ancient horrors come to life before our eyes as the youkai hunter wanders the land to find proof for his theories.

This is a 1978 compilation which includes the previously published Morohoshi stories published between 1974 and 1976, they are collected in the following order:
1. The Black Investigator [ 黒い探究者 ]; Weekly Shonen Jump #37 (1974)
2. Red Lips [ 赤い唇 ]; Weekly Shonen Jump #38 (1974)
3. The Tree of Life [ 生命の木 ]; Weekly Shonen Jump Special August Issue (1976)
4. The Masked Face in the Dark [ 闇の中の仮面の顔 ]; New story realized purposely for 1978's Yokai Hunter tankobon edition
5. The Living City [ 生物都市 ]; Weekly Shonen Jump #31 (1974)