I am very intrigued by the way “true name” are handled in Haibane Renmei. It seems to differ from the usual name/true name duality found in fiction and myth, the as in Wizard of Earthsea (to take one particularly well-known example). In HR, there is only a root name from which the Haibane’s name is derived and interpreted. How that nameroot is interpreted is a function of the expression of the Haibane’s free will – the choices they make as they face their trials. The interpretation is the true name.
Granted, the form and spelling of the name changes for a Haibane, but to take Reki’s example she was still Reki – only Reki as in “ga-reki” and not Reki as in “reki-shi“. The interpretation of “Reki” as either “reki-shi” or “ga-reki” is the key, and the symbols within the Wall changed to reflect the interpretation. But Reki was Reki to the end.
Yukiusagi commented that Rakka seemed to know her true name already. I think that it was more likely that she simply understood the meaning immediately, since she had her true name revealed to her after she has escaped the circle of Sin, and was terefore enlightened. Reki, in contrast, was still in the circle of Sin and her true name was still indeterminate; there were two possibilities, dependent on the outcome of her choice.
Do Haibane who are not sinbound even have true names? Clearly there is some difference in significance of the true name for a Sinbound Haibane as opposed to a regular one (like Kuu, whose true name Rakka sees within the Wall but doesn’t recognize until she also hears Kuu’s laughter).