As it happened, Luna had not checked her cores, or really thought about anything except her physical reunion with Kane. So, she shook her head, before doing exactly that with a curious look in her eyes. 

She focused inward and felt around for the strength of her cores. Suddenly, her eyes snapped open wide. "Woah!" she exclaimed, before telling Kane what she found. "My soul core has advanced to the second rank, and my blood core has made progress to the fourth rank!" 

She quickly recovered from her shock, and looked at Kane with a sceptically raised eyebrow, "Don't tell me that actually happened during sex just now?" 

Kane grinned smugly, and shrugged, "What? Is that the weirdest thing my 'strange pink sex rune' has done since I got it?" 

Luna opened her mouth for a moment, but then closed it again. Her eyes narrowed thoughtfully, and she recalled what happened with Alexa and herself. So, she pouted, "No, I guess not…" 

Then, she started growing excited, her green eyes twinkling with glee, "But that's still crazy! Can we just get infinitely stronger by fucking now?! Because I'm onboard!" 

Unfortunately, her master chuckled, and shook his head, "I'm afraid not. The way Mána explained it to me is this: I can get stronger by having sex with women, but the benefits I receive are dependent on the woman's strength. I really don't gain much unless they're at least equal to me. In fact, if they're marked by me, I gain nothing." 

Luna dampened her excitement a little, and nodded to indicate she understood, "Alright, so fucking an army of weaker women isn't going to help much, guess that's fair. So, what about these marks then? And what about me? How did I get stronger?" 

Kane smiled softly. Despite Luna's desire to just follow him, rather than think about the big issues, she wasn't stupid. And he liked that about her. 

He continued explaining, "Apparently there'll eventually be a number of different marks I can place on people, but right not I'm limited to two: the Mark of Loyalty, and the Mark of Love." 

Immediately, Luna grinned happily, and knowingly, as she caressed the tattoo below her navel, "So which one am I?" 

Kane shrugged nonchalantly, "Loyalty, of course. The other one i— ah!" 

Angrily, Luna had sat up, wrapped her tail around his cock, and squeezed ever so slightly as she glared at him, "Which mark did you say?" 

There was no way the catling could harm his body without a weapon, considering her current strength, so Kane calmly chuckled. He grabbed her chin, and kissed his Valkyrie, until the scowl left her face, and her tail relaxed. 

"I meant to say love, of course," he whispered as their lips separated. 

Luna licked her lips and grinned at him, "You'd better have." 

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With that settled, Luna nestled back into his chest, "So what does this Mark of Love do?" 

Kane settled back against the wall and shrugged again, "Basically what you probably already expect. We can talk telepathically and having sex with you while you're weaker than me raises your strength, instead of mine. There is also one more thing, but I'll get back to that after I explain the rest." 

Luna didn't care about that, however. Instead, she focused entirely on the part he had told her. "Hold on!" she exclaimed excitedly, a wide grin on her face. "So, I really can reach the peak of Core Awakening stage just by fucking you?! What are we waiting for?!" 

Kane chuckled, and quickly pushed the catling back down after she already tried to insert him inside herself again, "Calm down. It doesn't happen that quickly, we should still take it slow to take care of your foundation, and we're not exactly in the best place for this. But we'll work on it later, alright?" 

Luna pouted aggrievedly, but nodded obediently anyway, "Fine… so what about this Mark of Loyalty then?" 

Kane smiled as he caressed the woman's back, "The sex is the same, in that it will raise their strength if they're weaker than me, but rather than telepathic communication, they have a restriction placed on them, which prevents them from betraying me in any way, and allows me to suppress their power whenever I like." 

Realization struck as the catling's eyes widened, "Ah! So, Alexa…?" 

"Probably bears the Mark of Loyalty, yeah," Kane nodded thoughtfully, finishing her sentence. 

After the realization passed, Luna frowned and cocked her head, "So what exactly determines which mark you place on them? And how?" 

Indulgently, Kane continued explaining, "The Mark of Loyalty is automatically placed during sex. The Mark of Love, on the other hand, only gets a chance if I consciously stop the Mark of Loyalty, but only actually forms if mutual love exists." 

Back when Mána explained this to him, Kane had realized that, if he hadn't deliberately stopped the rune from suppressing Luna's strength when they had sex in their appartement, it would have applied the Mark of Loyalty, rather than love. 

In other words, they were quite lucky, because with the wrong mark they wouldn't have had their telepathy, which would have made their world-hopping-adventure far worse. 

Regardless, before Luna could respond, Kane continued with a grin of expectation, "Fortunately, Mána has taught me a method of applying the Mark of Loyalty without sex, but only on willing targets. Through sex it could still be applied to someone unwilling." 

Luna nodded thoughtfully while internalizing this new information. Silence descended on them for a moment, before Luna finally grinned deviously, "Alright, so could we gather an army of women, and have you fuck some loyalty and power into all of them?" 

Kane chuckled, and shook his head, "That's a nice idea, but I'm not sure I have the stamina or time for that. I still need to focus on my own strength, after all. Plus, the inability to betray me is not the same as being forced to follow my orders. They'd need to be willing to do that in the first place, then the Mark of Loyalty is a nice bonus." 

Then he shrugged, "Besides, you know how I feel about forcing a woman, so they'd have to be willing, too." 

The catling grumbled a little but nodded in partial resignation. Partial, because she then narrowed her eyes, "But we are doing something with this, right?" 

Kane smiled mysteriously, "Of course we are, but we'll get to that." 

Luna nodded approvingly, "Good. So can you tell me what else this Mark of Love is supposed to do now?" 

Kane nodded smugly, and smirked as he raised his hands, "Sure. Although I'm afraid this is just for my benefit." 

Luna's eyes widened when she saw a small sphere forming above each hand. One was sparking with blue-white lightning, and the other was a swirling mass of red liquid. 

"Those are my elements!" she exclaimed, astonished.