Otto understood that the more he killed, the more natural and proficient he became. The best way to master any Boxing Method is through combat, especially high-frequency, lethal combat. Often, killing one person holds more significance than sparring with ten!
Just the journey from the Plaza to the Church alone had elevated Otto's understanding of the Boxing Method by a notch. Continuing his killing spree from the entrance of the Church through the corridor to the inside, his Boxing Method became increasingly rhythmic. Casio's method of helping Otto rapidly learn the Boxing Method involved infusing him with Qi, akin to injecting part of the experience and knowledge directly into his body. During battle, the fusion of knowledge and experience accelerated.
Bang!
The ornate metal gate shattered on the spot, exploding into fragments.