That made me shiver. As in when you listen to a song and it makes you shiver and cry, type of shiver, not the cold shiver.
It was so cute. I adored the fact that Tonks was so determined to get what she wanted, and she managed to out-argue a Marauder, that takes some skill.
I also loved that you stated the reasons you feel Remus was included in the Marauders, as many authors/HP fans don't really think he would have fit in.
The way you wrote the kisses really pulled me in and captured my attention, after all, I am a sucker for romance! :)
I think my favourite line paragraph would have to be:
“Good,” he murmured softly. “You’ve signed a pact with a werewolf: you’re mine now.”
I pulled back in mock horror, “Wait, you’re a werewolf? I can’t be with you; what was I thinking?”
His eyebrows skyrocketed into his hairline.
I winced, “Too soon to joke?”
I don't know why, but it reminded me of the relationship between Bella and Edward in Twilight, New Moon, and Eclipse (which, if you haven't read them, you should!). Which I absolutely adored because of the fact that he loves her even though he knows he shouldn't and he warned her of the danger he could inflict on her. I suppose that makes their relationship like Harry and Ginny's too as Harry left Ginny "for her own safety", just as Edward left Bella. Oh, and Remus left Lily in DH.
As you asked for some constructive criticism, I suppose I should mention a few things I noticed - to me Remus seemed totally in character, but at times Tonks wasn't quite perfect. I know sometimes people change when they fall in love with someone so unlike them they're the same (if you get what I mean), but I think some of the lines she said were slightly OOC. Personally, I quite like that as it adds your own opinion of the characters, but you could slightly alter her to make her match the books for any canon-freaks (as I call them! This isn't an insult, I'm a canon-freak! Lol).
Also, Tonks' little speech was rather ... wooden. The things she was saying was really cute and amazingly in character, it's just the order of which she said them, and the way she said them, that made it slightly formal.
Besides those two points, I really liked it. Well done! :D
Oh, and sorry for the wait for the review! 7/10