I Didn’t Mean to Save the Villain [Novel]

'I really chose well when it came to reincarnation.'
Is this compensation for a past life in which I never received a shred of love?
I've been reborn as a slightly weak (?) side-character princess in a drama-filled romance fantasy.
So what if I lack the holy power everyone else has? I've got the full "diamond spoon" package!
Now that it's come to this, the original story must not fall apart.
I'll preserve this golden age,
and secretly help along the leads' tangled, desperate romance!
***
Without any holy power of my own, I lead the "Shadow" knights to root out villains, help the hero with a head full of flowers grow up splendidly, and nip in the bud every scheme that might make the heroine cry!
And so I kept the days peaceful…
"It's you again, Your Highness."
"Yes, me again. I know that's unfortunate for you."
But the mysterious second male lead — the mastermind — found out what I was doing.
And yet…
"…Were you on a date with the young heir of the ducal house?"
"Even if you're wary of me, you furrow those lovely brows so often… it makes me a little sad."
"…I thought I might get to see you this way."
Isn't this man supposed to be obsessed with the heroine?
Why is he obsessed with me?
Wait… what's with that look of longing?