Toyota aren't 'getting back' with Daihatsu - they've held a controlling interest in Daihatsu since 1988, and are now extending their controlling interest to full ownership.

Historically co-operation between the two companies dates back to 1967, and Daihatsu built, and still build, cars for Toyota under contract. For example: the Daihatsu Boon - sold in some markets as the Sirion, Subaru Justy, Toyota Passo; Daihatsu build versions of the Move kei car and Hijet kei van/pickup for Toyota, and these are sold as the Toyota Pixis.

Daihatsu also sell re-badged versions of Toyotas in some markets - eg a five seater version of the Toyota Prius+ is also sold in some markets as the Daihatsu Mebius.

It isn't that Daihatsu have built cars using old Toyota tech, they've shared development of componernts such as engines, etc. For example: the 1.0 litre engine used in the Sirion is a version of the same engine used in the Aygo, IQ and Yaris; the 1.3 engine used in the Sirion , Terios, Copen, etc and Yaris (generations 1 & 2) was jointly developed by Toyota and Daihatsu.