bundesliga.com has all the information you need ahead of a game bursting with sub-plots and intrigue...
Mainz grabbed their first win of the campaign with a hard-fought 3-1 victory on the road at Hertha Berlin last weekend, and will hope to maintain their unbeaten run by adding more points here. Dortmund have already lost ground in the title race after defeat on Matchday 1 and can ill afford another slip up so early in the season.
Nikolce Noveski is injured for the hosts, while Joo-Ho Park is away with the South Korean U-23 side. However, , signed from Dortmund on transfer deadline day, is set to feature. The 22-year-old enjoyed an impressive debut in Berlin last weekend and should retain his starting place.
Dortmund are without Nuri Sahin, Marco Reus, Ilkay Gündogan and Mats Hummels, while (l.) is a doubt. Jürgen Klopp, returning to the club whom he led to Bundesliga promotion back in 2004, even admitted Hofmann would have been in his plans. "If Jonas was still with us, he'd probably be in our team."
Top scorer this season and Japan's greatest Bundesliga striker, Okazaki is undoubtedly the man on whom BVB will need to focus. The 28-year-old now has 28 top-flight goals and has notched 18 in 36 league appearances since joining Mainz in the summer of 2013, including a brace in Dortmund back in April.
Lining up against Okazaki is his namesake , who enjoyed an equally memorable Matchday 3. Two years after leaving Borussia, it was as if he'd never been away, as he bagged his 22nd Bundesliga goal against Freiburg. Rested during midweek because of cramps, Klopp will be hoping the 25-year-old can feature.
Hofmann: "It's going to be a special game. I've texted him [Klopp] to wrap up warm!"
Klopp: "I love coming back to Mainz and I love to see them do well, but twice a year I want to beat them."
In spite of a long list of absentees, Dortmund are riding high at present. They followed up last week's win against Freiburg with a superb performance and convincing 2-0 victory over Arsenal FC in the UEFA Champions League, and will look to check Mainz's momentum after the 05er's maiden season win at Hertha.
Die Schwarzgelben have an intimidating recent record in this fixture, having won eight of the clubs' 16 league meetings, including the last six. Both matches were close affairs in 2013/14, however, with Pierre-Emerick Aubameyang (l.) bagging a stunning free-kick to give BVB a 3-1 success at the Coface Arena.
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Alongside the two Shinjis, there have been plenty of Japanese players to have made a mark on the Bundesliga. Here's bundesliga.com's top ten, courtesy of the official Bundesliga YouTube channel: