As reported by 4Gamer, the company is launching the earbuds in limited quantities on December 22nd at 3 pm Japanese time and will sell them for 15,500 yen (£85 / $108) each. They're based on the company's CP-TWS01A wireless headphones.
According to 4Gamer:
The collaboration model announced this time features the Mega Drive and Dreamcast symbols on the earphone housing, and the charging case has the same design as each game console. Another highlight of the earphone notification sounds is that the Mega Drive model uses the Sega sound logo as the startup sound, and the Dreamcast model uses the system menu operation sound as the system sound.
That's not all that Onkyo has up its sleeve; it's also releasing wireless charging pads, acrylic stands and t-shirts as part of the collaboration with Sega.
All of these products will sadly be exclusive to Japan, but keep your eye on importers like Play-Asia, as they often have this kind of thing in stock.