The temptation was too strong to resist. The feeling of her breasts so full and heavy was enrapturing, as was the sight of Hitomi's massive chest heaving as she floated peacefully in the water. The orgasmic potential in their sweet output demanded to be explored and exploited; every fiber of her was screaming to push thus as far as was possible, and then to take one step beyond. This could very well end all possibility of leading a normal life - but nothing in her life on land could compare to this pleasure.
Diving in with the ferocity of an ocean preadator, she once again brought Hitomi's aching nipple to her mouth, eagerly sucking away to bring out the mana-like white substance held within her chest. At the same time, however, she lifted her own huge mammary up to Hitomi's mouth, practically shoving it inside. The girl needed no further prompting, letting out a moan of excitement before she began to pull at the teat like a vacuum cleaner.
It was a bit of an awkward position, requiring them to use their tails to keep close as hands were occupied with steadying enormous sacks of fat and milk. At first, it was a return to the mind-blowing haze of consuming each other's sweet mermaid product, but slowly, surely, something began to shift. The more they went at each other, the more magic flowed between them, driving up their pleasure and production in a cascading series of mystical interactions. With glee she could feel her own chest gradually taking on mass, and Hitomi's doing the same in her hands.
Slow at first, but as the feedback loop pushed further on, the pace began to pick up. With every moment it was becoming harder and harder to keep together, the sheer mass of their heavenly pillows pushing them apart, but still each woman held on. Before long, their faces were pressing deep into each other's bosoms, their minds hopelessly fixated on this endless cycle of pleasure and growth. Mary had no idea if there was any limit on their increasing mass, if they might well swell up to infinity - a part of her certainly hoped they could.
Hitomi, however, broke the loop suddenly just as they were reaching beach ball sizes, panting for breath. "Mary... should we..." She glanced down at the absurd size to which she had grown. "Ohh... if we go any further... our lives on land won't be possible anymore..."
"I could live with that," she replied, a hand gently caressing Hitomi's face as she stared into her lover's eyes. "Nothing but monotony and misery is waiting for us back up there. Down here... we could spend eternity in joy." Her other hand moved to grasp at Hitomi's tail, adoring the way the dolphinesque skin felt in her hand. "Please... embrace this with me."