Onegai☆Twins, Ano Natsu de Matteru Recommendations
this anime has same style) probably it willl be crossover)
it looks like ichika is a daughter of mizuho from onegai teacher? bsides alien look alike)
Both series contain a similar theme and feeling.
Both the protagonist present in the series are involved in a love triangle that has mishaps, trials, but also with joy and memories.
Both series are set in a similar setting filled with drama, romance, and emotions.
They have almost the same plot + written by the same person