Another of my finds last night under the signboard near Fukuoka University of Education. This small stag beetle is called a nokogiri-kuwagata, where nokogiri is the name of a traditional Japanese saw (for cutting wood), and kuwagata means stag beetle. This species shows a lot of variety in size and mandible shape. Because this male was pretty small, its mandibles were quite straight and with only small teeth, whereas a bigger individual would have curving mandibles with some larger protrusions. Here’s a picture showing the variety.
Prosopocoilus inclinatus = nokogiri-kuwagata (saw stag beetle)