Osamu Mikumo's Determination

Short Summary
''After Chika is cubified, Osamu makes it his mission to take her cube to the HQ in safety, swiftly dodging the Rabbits' attacks until Replica comes to his aid and summons Border's own Rabbit. Replica helps Osamu get to the base while Izumi, Yoneya and Karasuma stay behind to fight Hairein and the Rabbits.''

Adapted From

 * Chapter 69
 * Chapter 70