When Tonks kisses him, Remus does not know why this hasn't happened sooner, why he didn't do it sooner, because when she kisses him, it feels like there has been a piece of him missing all his life and it has just been replaced.
It is not like canoodling with Ravenclaw prefects in dark corners, like snogging over-friendly Gryffindors in the common room or like drunken kisses with a regretful Lily Evans, kisses to him that tasted like hope, homework and Jelly Slugs. The sort that were slow and gentle, so soft he wanted to cry because he was always so scared of hurting these girls, too frightened to enter relationships with them, too anxious to contemplate futures with them.
It is not like stolen kisses with Sirius Black, in seventh year and then later in the flat they share, rough hands roaming over skin and sweat seeping into the nooks and crannies between their bodies, when they are pressed so close in drunken nights that he believes that they may wake in the morning conjoined and he doesn't believe it to be a bad thing, kisses so intense that he could feel every atom in his body buzz, kisses that tasted like wet dog, desperation and Ogden's finest Firewhiskey. The type that flitted away in a storm of mistrust, traitors and war and even now he does not want to re-sample.
It is, instead, like serendipity and serenity, like words he found in Muggle dictionaries that sound so foreign yet delectable in his mouth, syllables that roll on his tongue, words like 'Nymphadora' and 'I love you'. These kisses are passionate, spontaneous, yet measured, kisses that she extracts from him and he can imagine that he is holding the entire world in his hand. Lips that send him to breaking point and back, chance, fate, fortune and destiny are all obsequious to him when she touches him. These kisses taste like health, happiness and Molly Weasley's chocolate cake and he wants more. He wants them for the rest of his life and he wonders why being a werewolf ever mattered. When Tonks kisses him, it feels like he is coming home.