So, you can pronounce Sun's kanji as "Haru", but if someone just hears you say "Haru", they can't connect it to Sun (because Sun in Japanese is pronounced differently (Taiyou)), unless they figure out it's a name and as a name it might use the kanji for Sun with a less common pronunciation (which doesn't mean Sun, that is). More likely they would connect it to Spring (the season, not your car's suspension). And the folks using this kind of writing system called the Europeans barbarians because Europeans didn't use such a confusing writing system.