There is no more 9-tailed Sparkleaf; there is only the 7-tailed Sparkleaf, and also the one-tailed Sparkleaf. As of July 15, 2016, the following information is current:
This is Sparkleaf's "true" form, so to speak. A feral kitsune, he displays his seven tails, tipped green to indicate his bond with nature; the five markings on his face indicate his servitude to Inari. Naturally, this is also the form in which Sparkleaf's fox powers are strongest.
In the past, Sparkleaf displayed his seven tails proudly and freely. Now, he safeguards this form more carefully, reserving it for special occasions such as staff banquets, and typically does not reveal it in public.
Sparkleaf's everyday form. Illusion conceals both his facial markings and his multiple tails, so that he merely appears to be a strangely-colored fox. To Sparkleaf, this one-tailed illusion is akin to part of his clothing.
Note that he does NOT merely hide six of his tails; all seven tails are seemingly converged into one. Should his tail be injured, his real tails will share the damage. However, it allows for much greater mobility and convenience. His tail is seven times as strong as a normal fox's, but he would not quite match the power output of another seven-tailed fox.
Only with a biped body does Sparkleaf retain the long scalp hair of a Ninetales. Just like with a quadruped body, he generally stays in one-tailed form, especially when wearing dragoon armor. However, he could theoretically appear seven-tailed and bipedal...
Bipedal Sparkleaf is comprised of multiple layers of illusion, sacrificing magical potential for agility and physical skill. Naturally, this is his preferred form for battle. However, it is also the most vulnerable to illusion-breakers.
As shown, Sparkleaf has seasonal forms, though they may not necessarily feature his markings. The winter form is now the only time his tails are 100% green. Additionally, as a staff member, Sparkleaf must sometimes employ various disguises, including foxdoge and Magical Vixen Sparkles.