To be honest I don't completely agree with your characterization of Naruto and Anko's relationship . Relationships are not static entities but are constantly evolving . They require effort by both the parties involved to maintain . They also require the people involved in the relationship to change themselves so as to fit their partners needs and expectations . Meaning that even the people involved in a relationship are not static entities either . Both the people involved in a relationship need to grow and evolve in a manner such as they can meet their partners needs and expectations . This is an ideal situation and is so not always possible . What generally happens is that one of the partner's has a more dominant personality which forces the other partner to grow in a manner to fit his/her needs and expectations . If neither of the above two cases is possible since both the people involved are too stubborn then the relationship breaks up over time .
A simple example being a girl forbidding her partner from going to the pub and meeting his buddies every day of the week .
A middle ground would be where the guy agrees with the girl to go to the pub only on weekends .
If the girl has a more bossy or dominant nature while the guy is more accepting he will stop going to the pub altogether .
If both the partners are stubborn in nature then these minor disagreements are known to cause break ups .
My gripe with Anko and Naruto's relationship is that both are inherently very dominant personality's which are too stubborn to change . I don't think a long lasting relationship can be created between such people . Naruto can't change thanks to him being the centre stone which holds his family together while Anko doesn't want to change . The only way a lasting relationship with these 2 people will be created is if Anko grows and evolves in a manner such that she can leave these parts of her personality behind (since Naruto can’t accept her as is thanks to his other responsibilities). If such is not the case then a long term relationship between Naruto and Anko is unfeasible .
Also I know Naruto trusts his precious people implicitly but I would urge caution about the number of people he informs about his relationships since as they say Loose lips sink ships .