Defeat everyone else in Anna's training mode.
Some enemies glow like Yoh when you have a defense up mushroom. This indicates that when you kill them, you will get their soul. If you see a glowing enemy, go out of your way to get them.
Use Corey and Gororo.
Use Shaolin and Leepai-Long. Jump into the air and press R or L. If you are lucky, one of your enemies will fly and knock another enemy out. This also creates a shockwave if you miss.
Use Korogashi, Enra-Enra, Kamaitachi, OniFireTama, and Jangalian.
Use Zenki and Kohki.
Use Jose, Pancho, Antonio, Zapata, and Miguel in the in the Spirit Menu Deck. Press L or R during the game to execute the move and a large dagger will appear across the screen, destroying enemies in its path.
Use Ian, Nizba, Dreisa, Yophia, and Frankensteiny. You must die with these spirits in your deck. You will return to the map with full health. Note: If you do not want to waste money on food, die intentionally to be fully healed.
Use Michael, Gabriel, Raphael, Uriel, and Metatoron.