I believe I wrote somewhere that I thought Jun sounded like a female name (unreasonable, I know, and I can't even remember what gave me that impression when I've always realized that Jun is a gender neutral name) and that I was glad in most instances (er...toku specific, actually) a fictional male Jun went by his last name. Well, thanks to the main character in this manga, now I think Jun is a cool name for both girls and guys alike. The kanji (or at least what I think is the kanji if the scanslator is to be believed) for it looks neat, too (seems like a character for 'thread' in there, but I guess I'm off on this one; it seems there might be more than one kanji to write this name, too). I'll just go look the meaning on this particular kanji up when I get a chance. (It's sad that I don't really notice that the name Jun has a kanji (or more) before, although probably because it's usually written in Kana as a (fictional) name.)
As for Shizuka, I never really took a particular interest in the name, except when I was remarking that a specific character is so not quiet when she has a name that was supposed to mean 'quiet' (or maybe it's more like 'peaceful'? Seems like it has a character for 'blue' in the kanji, or I'm mixing this all up, too. Oh well, one more word to go look up). Anyhow, if the definition I have isn't far off, I haven't met a fictional Shizuka who fit his/her name, yet (perhaps the one from 'Doraemon'? However, I don't remember her much). In any case, I feel like I would always have this manga's Shizuka in mind for a while whenever I think of the name.
Strangely, I don't think I'll ever end up naming my characters with these two names. Weird, since I usually use the names I like for my characters, but the associations (mental images I have) with the established characters who have the names are just too strong, particularly in Shizuka's case, because he's constantly referred to that way by the heroine.
純 (JUN) means pure, and never used alone except as a name, so no 'kun' reading. And yes, that's a kanji character for 'thread' on the left side.