It's noise from the HLA (hydraulic Lash Adjuster). You can try to service them/do bleeding/cleaning. There's a special mechanical tool that tests if a HLA is still in decent condition or not after cleaning them. Not sure if Mitsu SC here or any workshops have it. You usually need to use lighter engine oil like 5w40 or maybe even 5w30 to reduce the noise. Also do engine flush more regularly like every 15-20k kms. There used to be also a product from Wynn's that helped clean and silence the noise a bit when you add into the engine oil, but I don't know now if still got and where to buy.
The advantage of this is actually maintenance whereby you don't need to keep adjusting the valve clearance manually. If you do careful maintenance using good engine oil with the proper viscosity, the HLA will actually last quite long. Previously I owned 3 Mitsu before: 4G63, 4G67, and 4G93 across more than a decade and only once I needed to change the HLA and that was also during my very first ownership when I did not know much at that time.