A case study appearing in Forensic Science International, A fatal poisoning with 5-methoxy-N,N-diisopropyltryptamine, Foxy, is likely referring to this death. (thanks theobromus)

A death was reported in Japan in July 2004 which was initially said to be from an overdose of 5-MeO-DIPT. Although we have not found any confirming or additional details, the police have charged a man in association with the death.

Article in Japanese: Yahoo News Japan, Jan 2005

A summary of this by Lepanto:

On January 18th, 2005 the police charged a 36 year old man for intentionally providing a dangerous substance. The death occured in June, 2004 in Ibaraki (about 50km from Tokyo). The dose taken is not described, but they mention that a 'normal dose' is 10 mg, and the man charged knowingly provided a dose that was too high. The story also mentions that 5-MeO-DIPT is a "legal drug".

An unconfirmed description by osaru:

"I'm living near the area and the accident details were described in the local newspaper, which described dosage and route. The acccident happened to a gay couple in a small hotel. It was June 18, 2004 around 9 at night. A guy put 100 mg 5meo-DIPT to his partner's ass with a pipet. Although the guy giving the dose had noticed the average dose was supposed to be 10m, he had had an experience of 100 mg rectal by himself without any trouble, so he just thought to try same dose for his partner, just a bit of curiousity. After a while (not mentioned the exact interval but soon after it says), the receiver got sick and crazy. He was taken to the hospital and 3 and a half hours later, he died in the hospital. No details were given about the actual cause of death."

Unfortunately it seems unlikely we will be able to learn whether toxicology tests confirmed the identity of the drug in the man's system, exact mechanism/cause of death, or what dose he took. If anyone knows of additional resources that describe this death, please let us know.