Shin Megami Tensei IV

Shin Megami Tensei IV is the 4th mainline entry of the Shin Megami Tensei series of role-playing games. The game has a Pokémon style playstyle where the players collect demons to fight other demons. The game is far darker though, taking place in an apocalyptic Tokyo.

Gameplay
The game has the player go through dungeons doing various tasks that usually involve killing a demon.

Demon Gathering
Since the player initially has no demons, the player must convince demons to join with him. The player must first make negiotiations with the demon. Some demons need the Demonlingual app before they can be communicated with. The negiotiations consist of conversations based on the demon's personality and giving the demon gifts. Demons cannot be convinced to join your team if the player's demon stock is full or if they already have one currently in their stock. Sometimes, demons will join the player if he kills their compatriots fast enough.

Fusion System
This method is where the player will get the strongest and most demons. After unlocking the Mido app, the player can fuse two or more demons to usually make a stronger demon. The type of demon is determined by the races of demons used as well as their initial levels. The fused demon also gets its skills by the player selecting from the parents' skills in addition to a couple base skills