English (Source)
Enemy buildings can be occupied by building towers near the building. Buildings provide bonuses at the end of each wave depending on if it's partially, or fully, occupied.
Japanese Translation
敵の建物は、建物の近くにタワーを建てることで占拠できる。建物は、ウェーブ終了時に部分占拠か完全占拠かに応じてボーナスを提供する。