Concepts

 "Dude, you're so depressing." "Really?" "Yes. Literally every word you say sounds like you couldn't care less about dying." "...I see."

 A person looks down upon those who are direct with how they feel and what they say without reading the mood, but it is reading the mood that prevents this person from expressing themselves when they're hurt.

 In a world where it's survival of the fittest, two people form an unlikely friendship. Person A is average in strength and speed. Forms friendship with Person B because Person B seems slower than Person A, so if the need comes, Person A can leave Person B behind for whoever is attacking. Person B is unclear how much strength they possess. They appear helpless and cute, the kind of person you'd want to protect. This is, of course, an act. Person B acts this way in the name of self-preservation, calling on others' protective instincts to have them fight on behalf of Person B.

 Put the main character in a dress, with long hair and heels. Make them interested in fashion, makeup and flowers. Then, make them fall in love with a girl. By the end of the story, reveal that the main character was a guy all along.

 Long-tailed Manakins take on a "bad" student to dance with them. This is a symbiotic relationship. The bad student's dancing makes the original Manakin look much better in comparison, and the bad student gets to learn to dance better. Imagine that but in a group performance.

 Boyfriend and girlfriend, one of them is the main character whose POV the reader sees. MC believes that they are two halves of a whole, and is very dependent in their relationship. The other one, though, is of a healthier mindset and constantly tries to help MC become more independent. By the end, MC realizes that they are not two halves of a whole. Rather, they are two.

 The red-eyed tree frog, when threatened, flashes its red eyes at predators to startle them. While the predator is startled, the frog uses this chance to run away. Imagine someone who casts an illusion magic to make their opponent see someone startling, like their mother, and then the caster uses this chance to disappear.