The red Charizard represents Razewing Ratha, a dragon-like character with a red color scheme who can attack by breathing fire.
The Mii Swordfighter represents Leo, the male playable character of Monster Hunter Stories 2: Wings of Ruin who hatches the Razewing Ratha from an egg.
The Mii Swordfighter's Ninja Headband and black Ninja Suit, without DLC, references Leo's starting armor, the Karuma Garb which resembles a dark ninja's outfit with a headband.
The stage and music track represents the grasslands of Haloko Island, the main setting of Monster Hunter Stories 2, an entry in the Monster Hunter series.
Other trivia:
This spirit's Fire Attack ↑ references how the Razewing Ratha's fire attacks grow stronger as it grows older.
