Sincerity
Something you say to someone you become attached to should be said with sincerity. You need to speak with sincerity when you say things to someone who will eventually become your significant other, for example.
Imagine saying something with sincerity to someone you want to become important to you. Say something like, “I love you” out loud. Say it with the utmost sincerity.
せい
まこと
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When you say something with complete, unabashed sincerity your special saber (せい) starts to pulse with the beating of your heart. It shows the person you want to become close to that you truly are sincere!
Say, "I love you," again and watch your saber beating in time with your heart. If you weren't sincere it would fade and grow dull.