I only used to have nine pen!
Literally: exist – do / change – turn – strange
Alternately: Everything in the world is in a constant state of flux. Everything changes; nothing stays the same. A Buddhist comment on the fleeting and mutable nature of the world we live in.
Notes: U is an uncommon reading for the character 有, brought to us by the compound’s Buddhist origins. That said, the only phonetic variants of this phrase leave the initial character as it is, while the final character 変 can also be pronounced as ben or even as den.
This yojijukugo too comprises two two-character words: 転変 is “to change,” while 有為 is a more arcane expression referring to phenomena or events brought about by fate or karma. Note that this only applies to ui, though: homonym yuui means “talented.”