nice bike the cbr6. Re your chain, there's no short term fix. The chain goes loose as the front and rear sprocket gears wear. The links in the chain also wear. With this amount of wear as you accelerate you are making the problem worse. If you examine the peaks, the pointy bits, of the sprockets and they are sharp, they are definitely past their best. To stay riding the bike like this, you will strip all the teeth of the gears and therefore no drive.
Unfortunately the best way forward is to repace the chain + the front and rear sprocket (gears). To only replace the chain on old sprockets will wear out the new chain more quickly.
You will find when you go looking for a chain that the suppliers will offer you a kit. Just a chain can be as difficult to get.
A pain I know but the cb6 is a very popular bike and parts are readily available. Any other attempt to tighten chain would be dangerous and will only give you more grief and cost more in the long run,