godan verb (-su), intransitive verb
increase more and more; grow increasingly intense
Formal or literary intransitive verb describing a gradual, continuous intensification or increase. Often used with abstract nouns like 思い, 悲しみ, or 不安.
彼への思いはいや増すばかりだ。
My feelings for him only grow stronger and stronger.
不安がいや増
My anxiety continues to intensify.