Police in Hamamatsu were called after a "sweating and anxious" Collins went behind a shop counter and placed a knife on it in front of frightened staff.
When the first officer arrived on the scene and saw how big Collins was he immediately called for backup, Entetsu Department store division manager Katsuyuki Aono said. Police suddenly began to pour into the basement floor of the department where food is sold and soon there were more than 30 officers surrounding him.
"The Japanese police were very small in comparison to him and they must have been worried," Mr Aono said.
"But police did not have to physically restrain Collins and he was not handcuffed.
"They just walked him out of the shop normally, but there were 30 police surrounding him so it created a big scene."
Mr Aono said that when he first saw Collins he didn't realise he was a famous rugby player.
"We just saw he was a foreigner and was very, very big."
Collins is still behind bars more than a week after the bizarre incident. He could face up to two years in prison according to Japan's harsh weapons laws.
Although the 32-year-old has yet to be formally indicted, he is being held in custody for allegedly violating Japan's Swords and Firearms Control Law.
Collins' arrest certificate states he was arrested for carrying a 17cm "houcho (kitchen/carving knife) in public 'without a valid reason', such as for work purposes."
An eye witness said Collins had two knives - a survival knife and a kitchen knife.
Japanese weapons law differentiates between houcho, tsurugi (double edged swords) and katana (single edged swords).
If it is classed as a kitchen knife he could face up to two years in prison and a fine of 300,000 yen ($3796).
Restrictions on double-edged swords are the most strict and a weapon with a blade of over 5.5cm is prohibited. For single edged swords the size limit is 15cm. If Collins was judged to be in possession of a sword he could face up to three years in prison or a fine of up to 500,000 yen ($6328).
Marty Gibbons, owner of Aussie expat bar Liquid Kitchen, said Collins was a regular there and was never any trouble.
"Those guys are under the spotlight because they are representing Yamaha, so they usually keep out of trouble."
- Simon Scott
