添う
そう · sou · JLPT N3 · verb-godan
to accompany
👫 添 = add; 添う (sou) = add yourself to someone's side
添 also appears in 添加 (tenka, addition), so 添う means adding yourself next to someone: going along with them, or going along with their wishes. Sounds like sew: you stay stitched to their side. See also 寄り添う, to snuggle close.
添 — water radical 氵 + 忝 (phonetic)
添 is a phono-semantic compound. The water radical 氵 hints at the meaning 'to add water, to pour in more,' while 忝 supplies the sound. From the literal sense of topping up liquid, it broadened to mean 'to add' or 'to append' anything.