the_debt_of_time

"I get it," Harry said. "I feel the same way about Hermione. I meant what I said
tonight when you gave her that bracelet. She's my sister."
"I know, son," Sirius said, feeling a rush guilt for having stolen that from him. There
was no real guarantee that Mia would return in place of Hermione. Even if she did, he had
no idea how the witch would look at Harry: brother, nephew... maybe even stranger.
"So how did the two of you—?" Harry began.
"That's a story for another time." Sirius laughed, thinking of all the terrible and
amazing run-ins in the fifth-floor corridor at Hogwarts. "Maybe when you're older."
Harry rolled his eyes. "So what was she like?"
"Brilliant. Fierce. Merlin help anyone that crossed her. She was bloody frightening
when angry, and I should know because she was angry with me all the time. She was as
studious as your mother but had a wild streak like us. She was so smart when it came to
magic. She played some of the best pranks. One year, just because my brother punched
me, she and I sneaked down to the dungeons, and she put a modified Notice-Me-Not
Charm on the entrance to their common room."
Harry joined in when Sirius let out a happy laugh. "What happened?"
"They slept in the corridor until Slughorn came round to fix everything," Sirius said
with a grin. "She could change charms and alter potions and transfigure anything. When
she took her N.E.W.T.s, she beat out McGonagall's old record. Only Remus beat her exam
scores, and she often said he cheated."
"She sounds like Hermione," Harry said, his tone full of awe. "Except for the
pranking part."
Sirius snorted, feeling uneasy. "Yeah, she was... very much like Hermione."
Harry cleared his throat. "Sirius, I know you said it wasn't your place to say, and I've
tried minding my own business, but Hermione is like my sister. If my dad was as protective
over his sister as you say, it's only right that I do the same thing," he said and sat up tall in
his chair. "I don't know what it is, but I know something's going on with you and
Hermione, and I want to know what."
Sirius stared at him and did not make a sound.
"Sirius, if you're trying to replace your old girlfriend with―"