"Burger World": The Sharks hold everyone hostage at the eponymous eatery and threaten to kill her if Shohei screws up. What happens? Shohei gets Hikari II to help, and with its newly-grown vines, pwns Orin's flunkies, snatches his Katana out of his hand, and threatens him by chopping the table the Sharks ate at in half, which causes the gang to flee.
Hikari demonstrating her self-defense lessons on Sango in "Christmas".
"Cherry Blossom Birthday": Hikari's poodle Charlotte saving Shohei and Inumaru from Orin's doberman Wanikiba by biting Wanikiba's leg.
The ending of the final chapter tops all of those. After Shohei sacrifices his soul to save Hikari from Hikari II, the trio of women reveal their objectives and tell Hikari to use the ring that she from Shohei earlier after the trio gave it to him in order to weaken the plant. Then, nearly all of the souls that Hikari II ingested fly out of its stomach and retaliate.