Part of the journey is the end

his cover story is he's a jedi from another temple. they obviously sense some darkness within him despite his expert shielding. oh that? yeah, he got into some majorly traumatic stuff on a super secret undercover mission and when he was finally recovered by the jedi, they sent him back to coruscant to find balance and get proper medical help after the incident. its a perfect explanation for the suit, the fact that no ones heard of him before, and the darkness they sense in him sometimes. he's still trying to figure out if hes a sith or not.

obviously, because the force loves to laugh at him, no matter how dark and changed he is, he's always going to pair perfectly with anakin and obi-wan. he and obi-wan were the team, and anakin is literally him. of course they're going to match no matter how much he hates it. so he ends up constantly with them.

and as he expects, anakin hates him at first. and he hates anakin. anakin is also curious though, and he keeps asking about the darkness and vader is constantly rolling his eyes behind his mask because of course anakin wants to know about the dark side.

his plots to kill palpatine keep getting postponed because he has to keep his stupid cover story credible by going on all these missions and kenobi keeps trying to befriend him and have a nice chat over tea and can't you see im busy trying to plot murder? ill plot your murder next, see if i care (proceeds to care a lot)

sometimes anakin does do things that vader really hates. it happens often, actually, his self hatred doesn't come from nowhere after all. he's moody, and he's annoying, he's way too arrogant, he doesn't listen, doesn't learn. but also, vader can sense anakin's emotions super well because hes powerful as all get out and also that's literally him! and he keeps expecting all the darkness he thinks is just a part of him, but then all he finds is sadness.

vader had years to perfect covering up his insecurities behind arrogance and power, to cover his sadness with anger, to cover his fear with false bravado and recklessness. Anakin, comparatively, is so novice at it that its almost pathetic. in his memories, he may have thought he was always good at it, but looking at it from an outside perspective, vader sees so clearly past anakin's mask. and what do you mean he hasn't always been a bottomless pit of hatred and death?

meanwhile anakin is like. 12. vader has beef with a twelve year old and every time anakin makes a joke, vader catches himself laughing because they have the same kriffing humour and stop making me laugh you idiot kid im trying to hate you.

so then vader tries to hate anakin's weakness. all vader sees, all he wants to see is this naïve idiot who was to stupid to realise palpatine was using him and too weak to save the people he loves. but then anakin is smart, in the way kids surprisingly are. he's cunning when he needs to be, he's a genius engineer, he asks deep questions about the force amd who he is and his place in the galaxy. when they have the misfortune of crossing palpatine, anakin is genuinely happy to see him and vader cant even blame him because he's twelve and the chancellor is so friendly in a way that vader completely forgot about.

anakin's not just dumb weak little anakin, he's also the sum of all the people vader used to love, and in some ways still does. one time he quotes something shmi said in vaders vicinity and the sith nearly has an aneurysm because Stop Being Likeable. all the things he loved about luke, about leia? he sees them in anakin. he even sees similarities between ahsoka and anakin. between obi-wan and anakin. and to hate anakin is like hating all of them as well and how could he ever hate his family?

the worst part is that after a rocky beginning, anakin starts to like vader. he (mistakenly) sees obi-wan as this perfect jedi who could never understand his problems. and then there's vader. who is so similar to anakin, and apparently struggles with anger like anakin does, and "has been bound in chains for too long" or whatever he says in his random dramatic monologues? and anakin sees all this and thinks 'wow, a guy who understands and relates to my problems so well and still manages to be a jedi?' thats the most inspiring stuff ever! if vader can do this, then so can he!

so now whenever anakin feels he has no one to talk to about his darkness, he goes to vader. and vader is two seconds away from blowing his own cover because kid No im a Darksider dont come to Me with this wtf i cant help you.

so now anakin basically has two masters and the jedi just let it happen because hey they all seem to be working well together and it takes a village and they have nothing against some unusual master padawan dynamics anyway.

at some point vader accidentally mentions palpatine when talking about his 'undercover missions' (which has just become the carpet under which he sweeps all his oddities and trauma from his life as a sith) and anakin's like what? and vader panics and goes 'uh yeah palpatine was uhh sort of in charge of the mission' and then anakin becomes super offended on vader's behalf and is like 'how dare he send you on such a terrible mission' because at this point vader's had so much more time with anakin than palpatine, (who hasnt had the opportunity to manipulate him yet) and he resolves to never speak to palpatine again and vader's like... it was that easy to get this dumbass out of Sidious' clutches??? what???

vader protects anakin on a mission that went wrong and its entirely because he isnt ready to die of time paradox yet and he definitely doesn't care about anakin at all.

vader eventually finds the time to kill palpatine at last without getting caught and anakin's already 16 and what do you mean its been four years. and haha yeah im totally not a jedi regardless of the years ive spent acting like one its still all an act im not capable of being good like that.

also obi-wan keeps being super nice and grateful because 'i will admit that i didn't know how to handle a padawan all that well. i was one myself rather recently' and 'you've been very kind to help me with this, without qui-gon i didn't always know who to go to for help' and vader's just thinking Why are You being vulnerable with Me??? help. i'm awful, are you not aware? he finds out a lot about Obi-Wan that he hadn't realised before.

anakin still ends up losing his arm cause its like... a canon event for him or whatever and vader talks him through all the prosthetic stuff and is there to support him the whole time. he's still half in denial about caring about this kid while he lets anakin cry on his shoulder.