It sounds like you’re referencing a scene or a story concept:
The Setting: A crowded train (Chikan scenario), a common theme in Japanese adult media.
The doors hissed open at Shibuya. A wave of people surged out, and Mizuki used the momentum to give one final, sharp nudge with her shoulder, sending the man stumbling back into the seat of a very grumpy commuter.
Mizuki didn't flinch. Instead, a cold, sharp smile touched her lips. She had spent three years in a high-intensity Krav Maga stall, and she was tired of being a passive participant in her own commute.
: This is often the name of the lead female character. In these specific titles, she is typically portrayed as either the target of the "payback" or the one orchestrating it. High-Intensity ("Hot") Tone