Be it the Corrupting Heart, the nevermelting glacier, or the creeping branch, none of Them still exist today.
The Primordial Lifespring has already lost control. After Ishar'mla and Mizuki were both injured, He devoured the Firstborn one by one, and became the sole 'Absolute'. He converts all lives into resources, faithfully regulating them and ensuring their comprehensiveness. All existence is ever so neatly ordered– for almost everything that refuses to be part of this order has been eradicated. Humans failed to even erect their last line of defense, the ocean submerging the land beneath their feet in an instant. Terra is now the ideal ecosystem for the Seaborn.
In a corner of this vast paradise, the Seaborns once known as Mizuki and the Doctor hide in a cave, avoiding being annexed by the order. In such an ecosystem, names are disorder, nostalgia is disorder, and sorrow is also disorder.
What about the others? Amiya and Kal'tsit... How about the other Rhodes Island friends? Are there any survivors? Even being able to squeeze out thoughts like those is a luxury. Perhaps the only time when thought is worthy of those precious extra nutrients is when feeding is taking place.
The 'Doctor' wordlessly gnaws at the appendage Mizuki has just cut from his own body. At first, it would shed tears, whimper, and sometimes even cry hysterically while feeding. But these emotions and behaviors were clearly maladaptive to survival, and though it took some time, it eventually got over it. Or perhaps, it was finally engulfed by the enclosed environment and protracted silence and numbness that it was thrust in.
Mizuki cannot console the 'Doctor.' Of course, he knows that it is a bridge too far to offer his own flesh and blood to the Doctor so that it may live, but he is even less willing to accept the Doctor's death. Nevertheless, all the flowers, plants, mushrooms, and even the water source itself have been assimilated into components of the Lifespring, turned into shining specks of fluorescent light symbolic of the order He has woven, let alone the sea monsters that were once creatures. No longer is there any more 'normal' food. All of Terra has been absorbed into the glowing ocean itself. Mizuki is only barely able to decompose the special tissue he ingested into simple nutrients; that is to say, he may be the only 'safe' food remaining.
Mizuki does not expect the Doctor to accept his proposal at that time. Is it a result of survival instinct temporarily overwhelming the dignity of being human during extreme hunger? Is it because he does not want to die in front of Mizuki, to waste that which he snatched back from the jaws of death with his own life? No, the reason does not matter, as long as the Doctor can live on...
But for how long will these days continue, and for how long can they hold on? Mizuki smiles bitterly within his heart. He hopes that in a different time and a different place, the Doctor will not be reduced to this inevitable end with him.