"You know, I don't think I've thanked you yet." Isshin said.
"Pardon?" Rukia asked.
"I haven't thanked you yet," Isshin clarified. "For saving me and my family that first night."
"Ah that," Rukia inclined her head. "I did nothing. As you recall, Ichigo was that one who did all of the work. I just gave him the power."
"You don't have to be so modest," Isshin teased. "Without you, Ichigo would never have unlocked his shinigami powers. It was only because of you that he was able to save anyone."
Isshin shook his head, remembering that night. "I was powerless. A former captain who gave up his power to save the woman he loves. That night was the only other night that I regretted my decision. It was fortunate that you were there."
"But I-" Rukia stammered, blushing at the praise.
"I have a lot to thank you for, Rukia-chan," Isshin continued. "You helped Ichigo come to terms with what happened with Masaki. You helped him develop his powers. You helped my boy become a man. For all of those things I can never stop thanking you."
"It…" Rukia was at a loss for words. "It was what anyone would have done."
"And yet you were the only one who ever got through to him completely," Isshin pointed out. "Your presence changed him, it changed us all. Thank you Rukia-chan."
"You're welcome," Rukia bowed, not entirely certain what was happening.
"Also," Isshin's face took on a mischievous look. "Thank you for agreeing to become my third daughter!"
"Ah," Rukia said, uncertain about how to handle this side of the former captain since Ichigo was usually there to be a buffer for all of that. "It's nothing, really. You gave me a bed to sleep on and all."
"Of course I would!" Isshin replied, smiling broadly. "You and Ichigo shouldn't share a room until after the marriage of course. Call me old-fashioned but I think your brother would agree with me."
"Wha-?" Rukia was blushing, at a loss for words once more. Seeing Isshin laugh however, made her smile.
Okay, heads up. I think that at volume 1 chapter 1 Isshin was kinda feeling powerless that a hollow like that got the jump on him. I mean he was captain of 10th Division, you know? That thing was small fry. Anywho, I can't recall if Isshin actually thanked Rukia for this, so this happened.