masu
1.

To cause a quantity or amount to become greater than it was, resulting in a measurable expansion or enhancement in number or intensity.

2.

To experience a growth or intensification in a particular aspect, such as feelings, conditions, or levels, leading to a more notable state than previously existed.

3.

To surpass or excel beyond previous standards, indicating an improvement or enhancement in quality, performance, or attributes.

Example:

その知らせで彼の不安が増した。

いやiyamasu
1.

To grow stronger or more intense over time, often referring to feelings or emotions that become more pronounced.

2.

To escalate or amplify in degree or magnitude, particularly in a way that emphasizes or enhances a previously existing condition.