Be upfront! How else with Natsu?

"Let's go talk to her right now then!" Natsu finally declared, heading for the Guild Hall.

"What, just like that? No thinking things through?" Lucy asked, floating along after him.

"I don't overthink things! If she likes me, and we're going to make a harem, what's there to think about?" Natsu replied.

"... can't argue with that," Lucy grinned as they entered the Guild Hall again.

Natsu proceeded to march straight up to Lisanna, and asked, "Hey, Lis, how are you doing?"

Lisanna, who had been chatting with Mirajane and Elfman, jumped slightly, and looked up at Natsu. "Oh, hi Natsu, what's up?" she asked him cheerfully, a faint blush on her cheeks.

"Nothing much. Hey, Lucy has told me that you have feelings for me?" Natsu inquired of Lisanna, who immediately went from faint blush to outright being able to enter her face into a tomato competition.

"You told him?" she whined to Lucy, who giggled and shrugged.

"Why wouldn't I?" Lucy answered with a question of her own. "You didn't exactly tell me in confidence, you know..."

"I didn't think I needed to spell out that this wasn't meant to be idle gossip, let alone told right to Natsu!" Lisanna protested. Mirajane and Elfman started laughing at their sister's misfortune.

"...oops?" Lucy asked in a faux innocent manner.

"Lucy!" Lisanna whined.

Natsu laughed a bit, and then said, "Anyway, I'm actually interested in you too."

She paused, going red in the face again. "...you, you are?" Lisanna asked, stunned.

Natsu nodded. "I am. What do you think? You interested in getting into an unorthodox relationship with Lucy and me?" Natsu inquired, uncaring of the fact that a good number of the Guild was watching in interest.

"Lucy and "I,"" Lucy corrected Natsu's grammar.

"Not the time!" he retorted, and she giggled.