[1] There were two kanji used for Heaven 天上界 Tenjoukai and 天空界 Tenkuukai. Ciel used the first one which can also mean Celestial World, while the other people use the 2nd one which would be closer to Sky World. 天空Tenkuu mean Sky but can also mean Heaven. I’ll just keep both as heaven. [2] 超強化 Choukyouka. Super/Ultra/Hyper Strengthening/Power Up/Boost. [3] Could be a pun. 丸くなった can also mean rounded. It also has the kanji maru in it. [4] This kind of eraser: (Also known as putty rubber)

[5] 知性珠之神剣(インテリジェンスソード) Chisei Tama no s.h.i.+nken (Interijensu Sōdo). Divine Sword with Intelligence Orb/Ball/Sphere.