SMT stands for Shin Megami Tensei (真・女神転生). It is a popular RPG series introduced by Atlus.
SMT is designed as an RPG with a deep story line that can be enjoyed by adults. In Japanese, the series is also abbreviated as "Megaten". The stories of SMT usually employ a real social setting as the stage, and present various contradictory human values including destruction, creations, law, and chaos, etc. In addition, SMT also features a system that lets the characters communicate with demons, and even recruit them or create new demons through fusion. This system imparts a characteristic immoral flavor to the series.
According to Atlus (JPN) the SMT series includes:
1) Shin Megami Tensei
2) Shin Megami Tensei II
3) Shin Megami Tensei if…
4) Shin Megami Tensei III - Nocturne