When Kohaku arrived she looked so bright and confident I feared her light would completely envelop Hitomi. But instead of a bright sun blinding everything else in its vicinity, Kohaku proves to be a warm sun, embracing Hitomi just as her granny would…because she is her granny. She takes that role very seriously without pulling herself out of her own present.
Immediately, Kohaku attracts a lot of attention, especially when she “transports” her class to England by casting an illusion spell that puts the class into a photo. It would seem her penchant for causing mayhem at school rears its head when an illusory steam locomotive covers everyone with soot and smoke.
That night, at the ridiculously awesome Tsukishiro residence, Hitomi and Kohaku talk before bed, about how Hitomi not knowing precisely why she’s there or for how long, in other words not knowing what will come next, is exciting. She also shows Hitomi a photo of a train that was in the album she held; the magic train was her doing; she has magic power, it’s just hidden and dormant, only coming out under certain circumstances.
And for all the havoc she’s wreaked over the years, Kohaku maintains that magic should only be used to help people and to make them happy. She considers magic to be a gift from God, and its the duty of every mage given such a gift to give it back to the world through happiness.
The photography arts club is a happy bunch, with Chigusa and Kurumi slowly growing together (though Kurumi puts on a front of loathing and Chigusa pretends to be aloof). They go on the high school roof at night to take photos of the skyline.
Yuito tells Hitomi that seeing only in monochrome can have its advantages. She’s able to see or understand things color normally obscures for everyone else. The gang also learns that Hitomi is Kohaku’s granddaughter from sixty years into the future…and they’re perfectly fine with it (for the most part).
The two Tsukishiro mages cap off the night by transcribing Yuito’s tablet drawing of a train into the sky. They’re using magic to help their friends by making them happy. The next day while going over their shots, Kohaku officially joins the club and adds “magic” to its name, making it the “Magic Photography Arts Club.”
Rather than someone who was going to shove Hitomi out of relevance, Kohaku is a net positive to the group, strong and self-assured in every way Hitomi is not, but also warm, generous, and loving. Knowing Hitomi is from the future worries Yuito, because he doesn’t know if or when she’ll return there. I imagine such worries are premature; Hitomi still has a lot left to experience in the past.