Yakusoku is a temperate E-Class world operating as the capital of The State of Tenshi, a fairly large state within the Confederacy of Borealis. The planet has a small population of 1.2 billion, however, these 1.2 billion people together have one of the highest concentrations of wealth on a single planet in the known universe, with an estimated 176 Septilllion C-Units divided among these individuals. The planet is located within Kanadett, a star cluster in the Via Sagittaria Galaxy.
The planet is entirely hollowed out, with a framework of active support holding the ten-kilometers of crust up over the core. The core itself was replaced with several layers of radiation shielding and a black hole. The black hole itself has a small accretion disk which acts as a power source for the planet, its potential output rivaling that of its parent star. The black hole was originally constructed when the State of Tenshi was in case of a siege. In the event of an emergency, the black hole is capable of emitting a small quasar that can be weaponized. Most of the defense infrastructure on the planet was built during a more turbulent time of the galaxy. Many recently colonized planets do not have such extensive (and more importantly expensive maintain) defensive structures.
Even with the defense structures, the large concentration of wealth on the planet warrants extra precautions. The Nobility has has vast numbers of ships from the State stored in the system, capable of responding in minutes to a threat. They are designed to defend the planet long enough for the most important individuals to escape while allowing for a large fleet to eventually return to bolster the planet's already extensive defenses. A large portion of the energy of its star, Senta, is devoted to a high-energy laser array capable of vaporizing any covalent bond from over an astronomical unit away. Senta is a very luminous star, allowing for a large number of energy-intensive infrastructure to be built around it. This Beam, a variation of a Nicoll-Dyson beam, is one of the most powerful weapons of its type in the Via Sagittaria.
The planet itself is covered in large nature preserves with flora and fauna similar to those found on Aegyn. While virtual reality is enough for the average person to experience nature, those that can often appreciate "natural" beauty over the artificial.
Yakusoku has three major continents, Datte, Gerin, and Nepputsk accompanied by hundreds of smaller islands. None of these continents were present when the planet first formed as terraforming typically disrupts planets so much that even the largest natural structures are often changed beyond recognition. What little magnetic field the planet had was destroyed by the hollowing out of the planet, so it is protected from damaging rays by a large array of magnetic field generators orbiting it.
The oceans are filled with artificially enhanced coral designed to live in not just shallow water but across most of the ocean floor, creating stunning reefs near the surface and equally stunning bioluminescent reefs towards the bottom. Large kelp forests fill more temperate areas of the sea floor.