@Jimbobjoe The mess called the 'Water God' is currently A.W.O.L. and even his direct subordinates can't get a hold of him. The one who asked Takumi to do it is the chief retainer (secretary) of the water god and chose him because he was already close enough. Kaiser was far away at the time.
@Jimbobjoe - maybe that's why the wind god was angry? Normally, they should have relayed this job to Kaizer the Leviathan.
Still, I wonder how Kaizer managed to live this long without a name.
@flannan He's a giant Leviathan, so I doubt he'd find anyone he'd consider making a contract with very easily, and most would be too scared to even try and talk to him.
Also, maybe the name is contract-specific, so that he knows who is calling based on what name they use? I don't know how it's intended, but the way it was worded made me think that might be how it works. Or, a "temporary contract" could also mean that the name used is also temporary, as in the name loses its meaning when the contract expires.