Sharp-shooter Tonge tied down as he signs for Harborough Town
Tonge has been playing in the Vanarama National League North with Rushall Olympic this season, but has opted to make the drop back down to the Northern Premier League Midlands Division with the Bees.
Borough boss Mitch Austin has been a long-time admirer of Tonge, who last season played for Coleshill Town in the NPL Midlands, and was voted into the team of the season.
In all for Coleshill, Tonge scored an impressive 65 goals in 90 appearances, and Austin will be hoping the striker can replicate that form in in a yellow shirt.
"To have a player like Kai on board, a player I have long since admired, I am absolutely delighted," said Austin.
"Kai has caused us many problems when he has faced us previously, and he joins a great group.
"We can't wait to see Kai in a Harborough Town shirt doing what he does best - scoring goals."
Tonge could be in line for his Bees debut on Saturday when Austin and his team travel to Hinckley LRFC for an FA Trophy second qualifying round clash.
Town will travel in good heart after an heroic effort in Saturday's FA third qualifying round ended in late heartbreak at National League North leaders Tamworth.
The Bees were reduced to 10 men after just 21 minutes following the dismissal of Connor Kennedy for two yellow cards, but then took the lead through Paul Malone five minutes later.
The home side took until the second half to equalise, and then netted an 89th-minute winner to break the Bees' hearts.
"I am so proud of the work rate and effort from my step four side against a top of the table team in step two," said Austin. "That is the magic of the FA Cup - roll on next year.”
RUGBY: Market Harborough claimed their second win in the Regional Two Midlands East with a 41-21 home success against Olney on Saturday.
Borough are up to fifth in the table, five points adrift of 100 per cent leaders Old Scouts. On Saturday, Borough travel to Wellingborough.