If it is 存款証, it should be CD (certificate of deposit). Not sure deposit link = CD. Maybe the bank here like to name it as other way to attract investor.
Feature of CD is closer to a bond but with shorter maturity. So it is not under DPS. They should have min purchase size and min increment size as well.
There is 2nd market for CD. So you may be able to sell the CD back to market. Ideal case it will include the accrual interest even I doubt :)
If deposit link =/= CD, I will guess it is kind of currency link deposit or deposit link mortgage ?! Anyway, need to see through the detail to ensure if there is any trick.
To me: This kind of mortgage link is kind of spare loan @ mortgage rate. Unlike other mortgage, you can repay the "loan" at any time you like by just deposting money to the account. So it offered us extra flexibility. I checked last time that the overall mortgage rate is a bit higher than the normal mortgage rate. Think this makes sense. I have not checked the detail but i believe there should be extra charge in mortgage rate or other form for the bank to offer us extra "flexibility".
So my conclusion is that no harm to take it if you need this flexibiity.