Richter Strategy:
The Werewolf is your first boss. He has two main attacks: a lunging claw attack and a high jump. Stay at a medium distance, whipping him as he approaches. When he jumps, you can often slide under him with a backflip or simply move to the opposite side of the arena. The Axe sub-weapon is highly effective here, as it can hit him even when he's airborne or during his lunge. If you have enough hearts, an Item Crash with the Axe can deal significant damage and stun him briefly. Focus on dodging his lunges and counter-attacking immediately after he lands or finishes an attack. Don't get cornered.
Maria Strategy:
Maria's speed and double jump make this fight easier. Use her Doves to attack from a distance. When he lunges, double jump over him. Her Cat sub-weapon can deal continuous damage if he stays on the ground. The Dragon sub-weapon is also effective for hitting him during his jumps. Maria's Item Crash (Music Box) will decimate his health if you have enough hearts. Stay agile and keep your distance while pelting him with projectiles.