I wasn't aware Sei-Lan from Angelique was a rip-off until I saw this photoset on an acquaintance's blog. Pet Shop of Horrors was first published in early 1995 (at least in compilation, which means it was probably running in magazine format for a few months prior); in late '96, Angelique Special 2 came along. The chinoiserie; the enigmatic attitude; the longish bob most often in the blue-purple range Sei-Lan favors - it's all there in Count D, Pet Shop's central figure. The two bottom images in particular seem to be part of the inspiration for Sei-Lan's music video from the OVA 3 series, which largely concerns him wearing airy white shirts, posing in water, and following a monarch-like butterfly that probably represents artistic inspiration or some damn thing.
I'd heard of Pet Shop of Horrors but wasn't aware it was popular enough for its characters to spawn imitators - perhaps the nature of the Count D character just filled a hole in Special 2's cast. I watched the second episode of the anime adaptation (bailing on the first after I learned the unfortunate direction it was going), and Count D does have Sei-Lan's ambient smarm down. He knows all (or thinks he does), but you're probably not worthy to be let in.
That is a very Sei-Lan thing to say as he's trying to convince you to buy poison.
I will say that Sei-Lan, for once, has a moral leg up on the competition. Pet Shop of Horrors is Gremlins with bishounen: D runs a Chinatown pet shop stocking mystic creatures, which he sells contingent on three contractual rules designed to prey on the prospective owners' character weaknesses. The consequences of their inevitable contract violations are designed to teach the owners a moral lesson, which is of dubious value, as the owner usually winds up dead. In the episode I saw, D's target was a man whose great crime was feeling depressed that the woman who forced him into an arranged marriage committed suicide when she learned he didn't actually love her. D helps her (now reincarnated as a mermaid) attain her revenge, even though the episode makes it clear that she is the aggressor and wrongdoer in the situation, having forced the marriage out of possessiveness and killed herself to inspire guilt. D's meant as a Rod Serling-esque framing device for anthologized horror, but he's a poor gateway character: his targets are largely victims, not evildoers, and his actions not retributive but sociopathic. The franchise seems the type that's remembered largely for its thrown-in homoeroticism - pairing D with a police officer on his trail who correctly believes he's culpable in multiple homicides - but they have no chemistry, and D's not the type you want to see inflicted on anyone.
Despite Sei-Lan's unfortunate inspiration, though, perhaps this zoophilist heritage does at long last provide an explanation for his inexplicable selection as the Guardian of Green.