You will get access to the Search and Destroy mission straight after speaking Takemura. He will direct you to safe house that he is in, telling you to knock on the door four times when you get there. Make sure you do this, or Takemura will think you are an enemy and kill you through the door.
When you enter, you will discover that he has brought Hanako there and you can make a deal to help her if she helps you. The dialogue options here don’t really matter much, the conclusion of the conversation is pretty much the same.
You will here a noise outside, so go and check the hallway. A cutscene will play, and Adam Smasher and some Arasaka goons will show up to extract Hanako. The floor collapses below you, and you will need to make your outside, or decided to save Takemura.
If you have the double-jump ability, saving Takemura is easy. All you need is jump back up through the gaps in the ceiling to the floor he is on, then wipe out the troops he is fighting. You can then both fight your way out, getting to safety. If you don’t have the double jump, make your way down the hall until you come to neon cross on the wall. Fight your way down the hall to the stairs, then head up two floors. Head down the hall and take the next right to get to Takemura and help him escape.
You can get an easy escape by just dropping down the holes in the floors below, ending up back where you started, then go back to the blue cross and turn right.
Getting Takemura out of the building can impact one of your endings, so you may wish to do it to give yourself the most possible options later in the game.