What happened?
The long relationship Toyota Motors (TM -0.52%) has had with its subsidiary Daihatsu is about to change. Both companies announced that Toyota, currently a bare-majority owner of its fellow Japanese vehicle maker with a stake of just over 51%, will purchase the remainder of the company. This will be effected in an all-stock transaction at an estimated value of $3 billion.

In Toyota's press release announcing the move, the auto giant said that its purpose was "to develop ever-better cars by adopting a unified strategy for the small car segment, under which both companies will be free to focus on their core competencies."

In 2015, Daihatsu's global sales fell by 13% on a year-over-year basis. This was the weakest performance among Toyota's units.

Toyota said it expects that Daihatsu's shares, currently traded on the Tokyo Stock Exchange, will be delisted in July. The transaction should close the following month.

Does it matter?
Daihatsu is not a huge part of Toyota at the moment, and still won't be when it becomes a fully owned subsidiary. (This past December, for example, it produced around 74,000 vehicles out of the total Toyota group figure of almost 800,000.) As such, this deal probably won't be much of a factor impacting the parent company's results in the short to mid-term.

But it's got potential. Daihatsu specializes in small cars, which, due to their price and form factor, are popular in relatively lower-wage Asian countries with strained traffic and parking infrastructure.

Further down the road, there is also potential in the European market, which is home to many municipalities that date back centuries -- and thus present traffic and parking challenges that make small-form cars appealing. Certain American municipalities have similar difficulties.

Speaking of the latter, very crucial, car market, Toyota could use a boost in market share -- which might theoretically be achieved through full ownership of Daihatsu, as it specializes in the small-form niche (an underdeveloped segment in the U.S.). In 2015, Toyota's overall slice of the U.S. car space remained unchanged (at 14.4%), while other Japanese manufacturers gained ground. Most notably, Fuji Heavy Industries' Subaru saw the biggest gain in share, to 3.4% of the market from 2014's 3.1%; Nissan, meanwhile, ticked upward to 8.5%, from 8.4%.

Those aren't worrying numbers, but they show that Subaru and Nissan inched ahead while Toyota remained in neutral. So, for the latter, perhaps being the sole owner of Daihatsu will help push it forward again.