 If you liked
Tenshi na Konamaiki
|
 ...then you might like
Fantasy Bishoujo Juniku Ojisan to
|
The main gist of the series are rather similar - a guy turns into a cute girl and in both cases are treated as "curses".
The rival of that guy either liked the person already previously or starts to have feelings towards the "new girl".
However, Tenshi na Konamaiki is not isekai while Fantasy Bishoujo is.