to go into; to come into; to penetrate; to get in; to step in (a house)
to become complicated
猫が箱の中に入り込んだ。
The cat slipped into the box.
風が窓から入り込む。
The wind penetrates through the window.
冷たい風が窓の隙間から部屋に入り込んでいる。
Cold wind is getting into the room through the gaps in the window.