It's a shame using "Shion" as a fanon last name for kaito has fallen out of style because it reminds people of their cringe early fandom days because it's actually a really good fan name. The kanji 音 present in Miku/Rin/Len/Lukas names is usually read as "On" so Shi-on actually works as a similar name without using the same reading. Shion is also the Japanese name of the flower aster tataricus, a light purple/blue flower whose meaning in flower language is "I won't forget you". Kaitos very own fanbase in Japan, by calling him Shion, promised they would never forget him. And even better? It blooms in August and September. The same time when Kaito started to get popular on Nico in the wave of Miku's release in 2007! (Ok that last one is almost definitely a coincidence)