None of their wishes made any sense, so I guess that justifies Dena's somehow making even less sense.   

Like where did those names come from?  

What happened to Thana's parents?  Apparently, Mai's parents were rich enough to move more than once in a short time period, and offer to let Mai live on his own.   But then as Thana, his mother needed money.

Then there's Nack.  His wish apparently took 10 years to fulfill, and only then after a night of heavy drinking.  It's like, dude, you didn't need a wish for that.

Your confusion is absolutely warranted.  A better name for the series would be "The Luminous Plot Holes."