Double Subversion: Justin dresses like a hobo, has dirty hair, and is sickly skinny, but then he gets cleaned up and turns out to be Beautiful All Along.
Justin thinks of himself as the most attractive guy in the world and expects everyone to fall at his feet because of it. Actually, he's not that hot and his ego makes him insufferable. Hilarity Ensues.
Justin is reputed to be extremely pretty. When we meet him, however, he's fat, hairy, and has little piggy eyes. Then it turns out that he's considered the hottest man alive in his home country of Gonklandia, where being fat and hairy with little piggy eyes is the epitome of physical beauty for both sexes. When he goes home for the holidays, he's met at the airport by a squeeing horde of fangirls who follow him everywhere.
Justin is the pretty boy of the show. His main personal goal is to break from his femininity by lifting weights and training in anything manly. But Alice and Bob usually angle to have him dress and style his hair to emphasize his prettiness for their personal gain. When Justin's Bishie Sparkles appear, he becomes a magnet for Gonks. Years later, he's still pretty but real buff! It doesn't stop him from looking good in a dress, though.
Or, take the Double Subversion where Justin is presented at first as unattractive, then gets cleaned up and seems Beautiful All Along, with Bishie Sparkles to match, and then cut to reality. He's still a Gonk.
Justin is unattractive, or handsome in a rugged macho way.
Expecting this trope in an anime targeted toward girls, the viewers are shocked to see not one single beautiful guy among the many males in the cast.
Enforced: "We need to attract the Estrogen Brigade demographic somehow. How about putting in a really pretty guy?"
Lampshaded: "Jeez, Justin is prettier than his girlfriend."
Invoked: Justin wants the girl he likes to fall in love with him, so he grows his hair longer, uses eyedrops to make his eyes sparkly, and gets the girl to meet him at the Botanical Gardens so he can ask her out against a background of roses.
Defied: Justin deliberately dresses poorly and leaves his hair messy so as to conceal his attractiveness.
Discussed: "Squee! ...Isn't Justin, like, the most beautiful guy in our school?"
Conversed: "All the guys in this show are unrealistically pretty! Why can't they cast some ordinary guys?"
Justin's girly features make him a target, as he is often harassed and mocked by people who call him a wimp and/or is thought to be gay, and, as such, is shunned/gets no attention from women. This really cripples his self-esteem.
His feminine features are due to a hormone imbalance or genetic defect.
Guys mistake Justin for a girl.
Justin is in fact Transsexual and people thinking of her as a pretty boy only adds to her anxiety - how she looks is due to hormones, and doesn't want to be complimented for looking a petty boy.
Justin being as pretty as he is leads people to set a standard of beauty for men that many cannot achieve, and he has a girlfriend who likes him for more than his looks. That Justin has set a standard leaves many men dateless and resentful of something they can't be.
...but his dating situation improves and so he doesn't do anything about his appearance.
Alternatively, guys still hate him but he gets more dates and attention from women than the other guys because of his prettiness.
Untwisted: A whole series of bishies is introduced...and at the end of the line is Justin, who dresses like a hobo, has dirty hair, and is sickly skinny, but gets his share of Bishie Sparkle and has his own fandom.