Finally getting time to reply to this post 😃
I hadn't really thought about the age difference between Anami and Adhiraj ... the fact that Anami is just 17 and underage was enough to not get me too invested in the love story yet. And Anami is definitely 17 ... that's the crux of the story. The love story is, I feel, only a small part of the show ... what will be important here is not the love part, but how it influences the dynamics between Adhiraj and the rest of the LM inhabitants.
Adhiraj is here for a purpose ... he has taken up the case for his own ends. When he discovers that Anami is actually the true heir it will change his feelings for her overnight ... not in the way that 'oh my god, she is the heir, I am a lowly commoner' ... but 'she is part of this family that I hate'.
Anami ... this part of your post ... I can see that happening.
Anami will fall for him, quite soon, I would say, this is obviously our couple. But because of the "shareefness" of the lead hero, we, the audience will see her blossoming into attraction, then an awareness of her femaleness, then a slow achingly sweet sense of liking. And we wont obsess over how young she is, to feel these things. Because 17 is hella young. But it will work, because the guy will not force it, will not encourage it, and he wont allow it to get crazy or creepy. She knows the truth, she is the heir. For her, nothing will change ... she has a crush on this hot guy, he's giving her some attention and like you describe him, he is non threatening, a very safe guy. I won't call it love yet ... at 17, it's a crush. It may blossom into love later ... but now for now.
Adhiraj will (has?) fallen for Anami. And because she reminds him of a "masoom," because of his job, because he has a younger sister probably Anami's age, he will keep a strict kaboo over his feelings. Perhaps even fight them. He will definitely not grab her or toss her up against the nearest wall. He wont make her feel ultra-feminine, or threatened by his masculinity. That is exactly the right casting, because most leading men of TV are instinctively sensual. They smolder, and you, an audience of ladies, you feel shy. But this guy makes you feel comfortable. And that's rare. He has a sister. He is an honorable officer. He has a female assistant he treats with respect and professional courtesy, every day.
So she will be bewildered by the change in his attitude when it happens. But then, she knows what he's thinking, that he doesn't believe she's the rightful heir, the real daughter ... right now, while she's enjoying his attention, she's also using him to help her fly away. However, she doesn't know yet that he hates the family ... that he has his own agenda. When she finds out, that will coincide with Adhiraj's change in attitude. A lot of dynamics will shift at that point.