[DeepL Translation - needs review] Aoyagi Rikka, a sixth grader, has lost the only person who understands her when her older brother Kiyoaki was killed two years ago. Then, she is visited by Wagatsuma Kusatoh, a "fighter" who used to fight with Kiyoaki as his master (Sacrifice). Rikka learns that Kiyoaki was killed by an organization called "Natsu no Tsuki," and together with Kusatoh, they challenge the battle and get to the bottom of her brother's death.
(Translator: DeepL)
There are fighting sections where spells with advanced vocabulary are used. Personally, I skimmed through them.
If you care about furigana, beware that it randomly disappears for the entirety of chpter 4. It seems that volume 2 takes a mixed approach, putting furigana only in relatively uncommon words.