Often, the setting plays a big role. It could be a battlefield, a post - apocalyptic world or a crime - ridden city. The soldier is always in his element in these tough settings and uses his knowledge and strength to save the girl. The girl, on the other hand, might be a civilian caught in the wrong place at the wrong time. Their encounter then becomes a catalyst for a story full of action, drama and sometimes romance.
One common element is the dangerous situation the girl is in. It could be anything from being held hostage to being in a life - threatening natural disaster. Another is the heroic entrance of the soldier, all brave and ready to save the day. And often, there's some sort of connection or relationship that develops between them after the save.
One common plot element is that Harry is in an abusive situation, which could be at the Dursleys' or within the wizarding world in some dark corners. Blaise then discovers Harry's situation. He might initially be hesitant but eventually decides to help Harry. There's often a slow - burn romance that develops as Blaise gets closer to Harry while protecting him.
Often, there is also an emotional aspect. Naruto might be motivated by his love for Sakura (even if it's just platonic in some cases) or his sense of duty towards her as a teammate. This emotional drive gives more depth to the story. And sometimes, the act of saving Sakura can also be a turning point in the relationship between Naruto and Sasuke, leading to either more conflict or a chance for reconciliation in the fanfic.
Well, perhaps the girl is a hunter too. She meets Dean in a really dangerous situation, like when he's being attacked by a powerful demon. She uses her unique skills, maybe some kind of magic she has been hiding, to save him. And from that moment on, Dean starts to see her in a different light, and a love story begins.
In a 'soldier saves girl' fanfic, it might be that the girl is in a natural disaster zone. The soldier, with his training and sense of duty, comes to her rescue. He might carry her to safety through floods or help her out of a collapsed building. This event could be the start of an interesting adventure for both of them as they face the aftermath together.
One common plot element is that Harry is usually in a vulnerable situation at the start. For example, he might be alone in a dark alley in the wizarding world.
One common plot point is that Percy discovers Calypso is in some sort of peril, like being trapped on an island or held captive by a powerful enemy.
Another element is the guy's motivation. It could be his sense of justice, his kind heart or even a growing attraction towards the ts girl. For example, he might see her in trouble and feel an instant urge to protect her. In some stories, the guy has been through similar situations before and doesn't want the ts girl to suffer as he did. And also, there is often a moment of connection between them after the saving. It could be a look, a shared smile or a simple conversation that starts a deeper relationship.
One common element is the unique characteristics of the monster girls. For example, a mermaid - like monster girl might have the ability to control water. Another common thing is the interaction between the monster girls and humans, which can range from friendship to romance.
A common plot element is that Piper gets into some sort of danger, like being trapped by a powerful enemy. Then Percy uses his abilities such as his control over water and his combat skills to save her.
A common plot element is Percy using his powers. For example, his control over water might play a crucial role in saving Zoe. Maybe he creates a water shield to protect her from some sort of attack.