The HTV-6 spacecraft had an extra mission after delivering cargo to the International Space Station, but it didn't work [space.com]:
After departing from the space station [space.com] on Jan. 27, HTV-6 spent a week orbiting the Earth 12 miles (19 kilometers) below and 23 miles (37 km) ahead of the ISS to keep a safe distance while testing out a new technology for removing space junk, or orbital debris, from Earth's orbit.
The Kounotori Integrated Tether Experiment (KITE) flunked its first orbital test [space.com] when a glitch prevented it from properly deploying a 700-meter-long (2,300 feet) electrodynamic tether made to grab pieces of space junk, the Japan Aerospace Exploration Agency (JAXA) reported Tuesday (Jan. 31).
JAXA's space-junk-removing tether [space.com] is designed to latch on to a piece of orbiting debris before pulling it down into Earth's atmosphere for a fiery disposal. The agency continued to troubleshoot and attempt to deploy the tether through Saturday (Feb. 4), but alas, the Japanese experiment burned up in the atmosphere without a space-junk tether success.